Mobile device

ABSTRACT

In the case where a temperature allowance of one translational mechanism of a plurality of the translational mechanisms (the electric motors  31 R,  31 L) larger than a temperature allowance of the other translational mechanisms, the operation mode of a plurality of the translational mechanisms are controlled so that the heat generation amount of the one translational mechanism becomes larger than the heat generation amount of the other translational mechanisms. By doing so, the difference between the temperature allowances of a plurality of the translational mechanisms is reduced.

TECHNICAL FIELD

The present invention relates to a mobile device.

BACKGROUND ART

The present inventors have proposed a control technology for an invertedpendulum type vehicle as a mobile device (refer to Japanese Patent No.3070015, Published PCT International Application WO/2008/132778, andPublished PCT International Application WO/2008/132779).

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, if the variation in heat deterioration lifetime is increasedbecause of the variation of accumulated load between a plurality ofmotors used in a vehicle and the like, lifetime of a part of the motorsis shortened. Therefore, there is a fear that a performance of thevehicle is deteriorated due to a functional loss of a part of themotors.

Therefore, the present invention aims to provide a mobile device capableof extending the heat deterioration lifetime of a plurality oftranslational mechanism which actuates accompanied by heat generation.

Means for Solving the Problems

To fulfill the object, the present invention provides a mobile deviceequipped with an energy accumulation component, a plurality oftranslational mechanisms for translational movement of the mobile devicewhich actuate by consuming energy accumulated in the energy accumulationcomponent, a first temperature measurement component configured tomeasure or estimate temperature of each translational mechanism, and acontrol device configured to control operation of each translationalmechanism, wherein the control device is configured to control operatingmode of each translational mechanism, in accordance with a temperatureallowance of each translational mechanism which is a difference betweena temperature of each translational mechanism measured or estimated bythe first temperature measurement component in the state being smallerthan a first temperature threshold value and the first temperaturethreshold value, or a sum of the difference and a proportional values ofa temporal change rate of the difference, so that a heat generationamount of one translational mechanism having large temperature allowancecompared to other translational mechanisms becomes larger compared tothe heat generation amounts of other translational mechanisms (firstaspect of the invention).

According to the mobile device of the present invention, in the casewhere the temperature allowance of one translational mechanism among aplurality of the translational mechanisms is larger than the temperatureallowance of other translational mechanisms, the operating mode of aplurality of the translational mechanisms are controlled so that theheat generation amount of the one translational mechanism becomes largerthan the heat generation amount of the other translational mechanisms.The heat generation amount of the translational mechanism is set inaccordance with the energy consumption amount of the translationalmechanism.

By doing so, the difference between the temperature allowance between aplurality of the translational mechanisms is reduced, so that frequencyof the temperatures of each translational mechanism elevating to atemperature high enough to promote shortening of the heat deteriorationlifetime is decreased. As a result, it becomes possible to extend theheat deterioration lifetime of each of the translational mechanisms.

The translational mechanism may be a translational mechanism equippedwith a mechanical braking mechanism for braking the operation thereofmechanically. An overall heat generation amount of the translationalmechanism may be controlled, by adjusting a kinetic energy of thetranslational mechanism which is converted to a heat generation energyby a dynamic friction of the mechanical braking mechanism, fromactuation of the mechanical braking mechanism.

The phrase that the control device and the constituent componentsthereof are “configured to” execute a given arithmetic processing meansthat a CPU (arithmetic processing device) reads out data and programfrom a memory, and executes the arithmetic processing according to theprogram on the basis of the read-out data. The phrase “configured to” isa concept including that the same is “programmed to” do something.

In the mobile device of the first aspect of the invention, the controldevice may be configured to control the operating mode of eachtranslational mechanism so that a difference between a ratio of the heatgeneration amount of the one translational mechanism with respect to atotal heat generation amount of a plurality of the translationalmechanisms and a ratio of the heat generation amounts of the othertranslational mechanisms with respect to the total heat generationamount of a plurality of the translational mechanisms becomes larger, asa difference between the temperature allowance of the one translationalmechanism and the temperature allowance of the other translationalmechanisms becomes larger (a second aspect of the invention).

According to the mobile device with the above-mentioned configuration,the ratio of the heat generation amount of each translational mechanismwith respect to the total heat generation amount of a plurality of thetranslational mechanisms is adjusted in accordance with the differenceof the temperature allowance between each translational mechanism. Bydoing so, the difference in the temperature allowance between aplurality of the translational mechanisms is decreased, so that itbecomes possible to reduce the frequency of the temperatures of eachtranslational mechanism elevating to a temperature high enough topromote shortening of the heat deterioration lifetime.

In the mobile device of the second aspect of the invention, the mobiledevice may further comprise an energy remaining amount measurementcomponent configured to measure or estimate an energy remaining amountof the energy accumulation component, and the control device may beconfigured to control the operating mode of each of a plurality of thetranslational mechanisms, respectively, so that the difference betweenthe ratio of the heat generation amount of the one translationalmechanism with respect to the total heat generation amount of aplurality of the translational mechanisms and the ratio of the heatgeneration amounts of the other translational mechanisms with respect tothe total heat generation amount of a plurality of the translationalmechanisms becomes smaller, as the energy remaining amount measured orestimated by the energy remaining amount measurement component becomeslarger (a third aspect of the invention).

According to the mobile device of the above-mentioned configuration, thedifference of the heat generation amount between a plurality of thetranslational mechanisms operating by consuming energy is reduced as theconsumption allowance of the energy accumulated in the energyaccumulation component becomes larger. By doing so, it becomes possibleto avoid the situation where the energy consumption amount, and furtherthe heat generation amount by the operation of a part of thetranslational mechanisms among a plurality of the translationalmechanism becomes excessive compared to the energy consumption amount bythe operation of the other translational mechanisms. As a result, itbecomes possible to reduce the frequency of each temperatures of aplurality of the translational mechanisms elevating to a temperaturehigh enough to promote shortening of the heat deterioration lifetimebecause the difference in the temperature allowance between a pluralityof the translational mechanisms is decreased.

In the mobile device of the first aspect of the invention, the mobiledevice may further comprise a braking mechanism which actuates to brakea translational motion of the mobile device, and a second temperaturemeasurement component configured to measure or estimate a temperature ofthe braking mechanism, and the control device may be configured tocontrol the operating mode of at least one translational mechanism sothat the heat generating amount of the at least one translationalmechanism decreases, and as well as to actuate the braking mechanism,taking the existence of a temperature allowance of the braking mechanismwhich is a difference between a temperature of the braking mechanismmeasured or estimated by the second temperature measurement component inthe state being smaller than a second temperature threshold value andthe second temperature threshold value, or a sum of the difference and aproportional value of a temporal change rate of the difference, as arequirement (a fourth aspect of the invention).

According to the mobile device of the above-mentioned configuration, thechange in the translational mode of the mobile device in accordance witha change in the operation mode of a plurality of the translationalmechanisms that decreases the heat generation amount of at least onetranslational mechanism may be adjusted according to the operation ofthe braking mechanism having temperature allowance. That is, thetranslational mode of the mobile device may be controlled so that thedecrease in the temperature allowance of at least one translationalmechanism is substituted by the decrease in the temperature allowance ofthe braking mechanism. By doing so, the difference in the temperatureallowance among a plurality of the translational mechanisms is reduced,so that it becomes possible to reduce the frequency of each temperatureof a plurality of the translational mechanisms elevating to atemperature high enough to promote shortening of the heat deteriorationlifetime. As a result, each heat deterioration lifetime of a pluralityof the translational mechanisms may be extended.

In the mobile device of the first aspect of the invention, the controldevice may be equipped with a desired total heat generation amountdetermination component configured to determine a desired total heatgeneration amount by the operation of a plurality of the translationalmechanisms, on the basis of the energy consumption amount of eachtranslational mechanism, a heat generation ratio determination componentconfigured to determine a heat generation ratio of each translationalmechanism in accordance with the temperature allowance of eachtranslational mechanism, and a desired heat generation amountdetermination component configured to determine a desired heatgeneration amount of each translational mechanism, respectively, byintegrating the heat generation ratio and the desired total heatgeneration amount, wherein the control device may be configured tocontrol the operation of each translational mechanism so that the actualheat generation amount coincides with the desired heat generation amount(a fifth aspect of the invention).

According to the mobile device of the above-mentioned configuration, theoperation of each translational mechanism is controlled so that the heatgeneration amount of each translational mechanism coincides with thedesired heat generation amount, which is a result of integrating thedesired total heat generation amount of all translational mechanisms,and the heat generation ratio, according to the temperature allowance ofeach translational mechanism. More specifically, the heat generationratio is determined to a higher value as the temperature allowancebecomes larger, and the operation of the translational mechanism may becontrolled so that the heat generation amount becomes larger. Incontrast thereto, the heat generation ratio is determined to a lowervalue as the temperature allowance becomes smaller, and the operation ofthe translational mechanism may be controlled so that the heatgeneration amount becomes smaller.

By doing so, the difference of the temperature allowance among aplurality of the translational mechanisms is reduced, so that it becomespossible to reduce the frequency of each temperatures of a plurality ofthe translational mechanisms elevating to a temperature high enough topromote shortening of the heat deterioration lifetime. As a result, eachheat deterioration lifetime of a plurality of the translationalmechanisms may be extended.

In the mobile device of the first aspect of the invention, a pluralityof the translational mechanisms may be configured from identicalspecification (a sixth aspect of the invention).

According to the mobile device of the above-mentioned configuration, theoperating mode of each translational mechanism and the relationship ofthe heat generation amount are common, so that it becomes possible toeasily adjust the heat generation amount of each translationalmechanism, in accordance with a differentiation of the operation mode ofeach translational mechanism and the like.

In the mobile device of the first aspect of the invention, the mobiledevice may further comprise a traveling motion unit which actuates atranslational force of the mobile device with respect to a floorsurface, while in contact with the floor surface, wherein the mobiledevice may be configured so that the common traveling motion unit isdriven by a plurality of the translational mechanisms (a seventh aspectof the invention).

According to the mobile device of the above-mentioned configuration, thedifference of the temperature allowance among a plurality of thetranslational mechanisms is reduced, so that each heat deteriorationlifetime of a plurality of the translational mechanism may be extended.Therefore, it becomes possible to reduce the frequency of disablement ofthe traveling motion unit from disablement of a part of a plurality ofthe translational mechanisms.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of an inverted pendulum type vehicle as oneembodiment of the present invention;

FIG. 2 is a side view of the inverted pendulum type vehicle;

FIG. 3 is an enlarged view of a lower portion of the inverted pendulumtype vehicle;

FIG. 4 is a perspective view of a traveling motion unit (wheel assembly)of the inverted pendulum type vehicle;

FIG. 5 is a diagram illustrating the placement relationship between thetraveling motion unit (wheel assembly) and free rollers of the invertedpendulum type vehicle;

FIG. 6 is a flowchart illustrating the processing by a control unit ofthe inverted pendulum type vehicle;

FIG. 7 is a diagram illustrating an inverted pendulum model expressingthe dynamic behaviors of the inverted pendulum type vehicle;

FIG. 8 is a block diagram illustrating a processing function related tothe processing in STEP9 of FIG. 6;

FIG. 9 is a block diagram illustrating a processing function of a gainadjusting element shown in FIG. 8;

FIG. 10 is a block diagram illustrating a processing function of alimiting processor shown in FIG. 9 (or a limiting processor shown inFIG. 11);

FIG. 11 is a block diagram illustrating a processing function of acenter-of-gravity velocity restrictor 76 shown in FIG. 8;

FIG. 12 is a block diagram illustrating a processing function of aposture control calculator 80 shown in FIG. 8;

FIG. 13 is an explanatory view in relation to an operation controlmethod of an electric motor; and

FIG. 14 is an explanatory view in relation to a control method of a heatgeneration ratio of the electric motor.

MODE FOR CARRYING OUT THE INVENTION

(Basic Construction of the Vehicle)

First, referring to FIG. 1 to FIG. 5, the structure of an invertedpendulum type vehicle in the present embodiment will be described.

As illustrated in FIG. 1 and FIG. 2, an inverted pendulum type vehicle 1in the present embodiment includes a payload supporting part 3 for anoccupant (driver) as a target object for transportation, a travelingmotion unit 5 capable of traveling in all directions (two-dimensionalall directions, including a fore-and-aft direction and a lateraldirection) on a floor surface while being in contact with a floorsurface, an actuator 7 which imparts, to the traveling motion unit 5, amotive power for driving the traveling motion unit 5, and a base body 9on which the payload supporting part 3, the traveling motion unit 5, andthe actuator 7 are mounted.

Here, in the description of the present embodiment, the “fore-and-aftdirection” and the “lateral direction” mean the directions that coincideor substantially coincide with the fore-and-aft direction and thelateral direction, respectively, of the upper body of an occupant aboardthe payload supporting part 3 in a normal posture. Incidentally, “thenormal posture” is a posture envisaged in the design related to thepayload supporting part 3, and it is a posture in which the trunk axisof the upper body of the occupant is oriented approximately in thevertical direction and the upper body is not twisted.

In this case, in FIG. 1, “the fore-and-aft direction” and “the lateraldirection” are the direction perpendicular to the paper surface and thelateral direction of the paper surface, respectively. In FIG. 2, “thefore-and-aft direction” and “the lateral direction” are the lateraldirection of the paper surface and the direction perpendicular to thepaper surface, respectively. Further, in the description of the presentembodiment, the suffixes “R” and “L” attached to reference numerals willbe used to mean the correspondence to the right side and left side,respectively, of the vehicle 1.

The base body 9 is provided with a lower frame 11, to which thetraveling motion unit 5 and the actuator 7 are installed, and a supportframe 13 extendedly provided upward from the upper end of the lowerframe 11.

A seat frame 15 extending toward the front from the support frame 13 isfixed to the top of the support frame 13. Further, the seat 3 on whichan occupant sits is installed on the seat frame 15. In the presentembodiment, the seat 3 serves as the payload supporting part for anoccupant (payload supporting part for the target object fortransportation). Hence, the inverted pendulum type vehicle 1 in thepresent embodiment (hereinafter referred to simply as the vehicle 1)travels on a floor surface with an occupant seated on the seat 3.

Further, grips 17R and 17L to be grasped as necessary by the occupantseated on the seat 3 are disposed on the right and left of the seat 3.These grips 17R and 17L are secured to the distal portions of brackets19R and 19L, respectively, which are provided extendedly from thesupport frame 13 (or the seat frame 15).

The lower frame 11 is provided with a pair of cover members 21R and 21Ldisposed to face each other in a forked shape with a gap therebetween inthe lateral direction. The upper end portions (the forked portions) ofthese cover members 21R and 21L are connected through a hinge shaft 23having a longitudinal axial center, so that one of the cover members 21Rand 21L is relatively swingable about the hinge shaft 23 with respect tothe other. In this case, the cover members 21R and 21L are biased bysprings, which are not shown, in the direction in which the bottom endportions (the distal ends of the forked portions) of the cover members21R and 21L narrow.

Further, a step 25R on which the occupant seated on the seat 3 restshis/her right foot and a step 25L on which the occupant rests his/herleft foot are provided on the outer surfaces of the cover members 21Rand 21L such that the steps extend out rightward and leftward,respectively.

The traveling motion unit 5 and the actuator 7 are disposed between thecover members 21R and 21L of the lower frame 11. The structures of thetraveling motion unit 5 and the actuator 7 will be described withreference to FIG. 3 to FIG. 5.

The traveling motion unit 5 and the actuator 7 illustrated in thepresent embodiment have the same structures as those disclosed in, forexample, FIG. 1 of patent document 2 mentioned above. Hence, in thedescription of the present embodiment, the aspects of the structures ofthe traveling motion unit 5 and the actuator 7 which are described inthe aforesaid patent document 2 will be only briefly described.

In the present embodiment, the traveling motion unit 5 is a wheelassembly made of a rubber elastic material formed into an annular shapeand has a substantially circular cross-sectional shape. This travelingmotion unit 5 (hereinafter referred to as the wheel assembly 5)elastically deforms to be capable of rotating about a center C1 of thecircular cross-section (more specifically, the circumferential linewhich passes the center C1 of the circular cross-section and which isconcentric with the axial center of the wheel assembly 5), as indicatedby an arrow Y1 in FIG. 4 and FIG. 5.

The wheel assembly 5 is disposed between the cover members 21R and 21Lwith an axial center C2 thereof (an axial center C2 orthogonal to thediametrical direction of the whole wheel assembly 5) oriented in thelateral direction, and comes in contact with a floor surface at thebottom end portion of the outer circumferential surface of the wheelassembly 5.

The wheel assembly 5 is capable of performing a motion of rotating aboutthe axial center C2 of the wheel assembly 5 as indicated by an arrow Y2in FIG. 4 (a motion of circumrotating on a floor surface) and a motionof rotating about the center C1 of the cross-section of the wheelassembly 5 by being driven by the actuator 7 (to be discussed in detaillater). As a result, the wheel assembly 5 is capable of traveling in alldirections on a floor surface by the motions combining the aforesaidrotating motions.

The actuator 7 is provided with a rotating member 27R and free rollers29R interposed between the wheel assembly 5 and the right cover member21R, a rotating member 27L and free rollers 29L interposed between thewheel assembly 5 and the left cover member 21L, an electric motor 31Rserving as an actuator disposed above the rotating member 27R and thefree rollers 29R, and an electric motor 31L serving as an actuatordisposed above the rotating member 27L and the free rollers 29L.

The housings of the electric motors 31R and 31L are installed to thecover members 21R and 21L, respectively. Although not shown, theelectric sources (batteries or capacitors) of the electric motors 31Rand 31L are mounted on an appropriate place of the base body 9, such asthe support frame 13 or the like.

The rotating member 27R is rotatively supported by the cover member 21Rthrough the intermediary of a support axis 33R having a lateral axialcenter. Similarly, the rotating member 27L is rotatively supported bythe cover member 21L through the intermediary of a support axis 33Lhaving a lateral axial center. In this case, the rotational axial centerof the rotating member 27R (the axial center of the support axis 33R)and the rotational axial center of the rotating member 27L (the axialcenter of the support axis 33L) are concentric with each other.

The rotating members 27R and 27L are connected to the output shafts ofthe electric motors 31R and 31L, respectively, through the intermediaryof power transmission mechanisms, including functions as reducers, androtatively driven by the motive power (torque) transmitted from theelectric motors 31R and 31L, respectively. The power transmissionmechanisms are, for example, pulley and belt system. More specifically,as illustrated in FIG. 3, the rotating member 27R is connected to theoutput shaft of the electric motor 31R through the intermediary of apulley 35R and a belt 37R. Similarly, the rotating member 27L isconnected to the output shaft of the electric motor 31L through theintermediary of a pulley 35L and a belt 37L.

Mechanical brakes 34R, 34L are fixed to support axes 33R, 33L that arerotational axes of the rotating members 27R, 27L, and configured tobrake the rotation of the rotating members 27R, 27L by pushing a brakepad which is driven by a piston against the disk rotating about theaxial center of the rotational axis.

The specification of each of the electric motor 31R and the mechanicalbrake 34R, and the specification of each of the electric motor 31L andthe mechanical brake 34L constituting a left functional unit 30L are setto be the same.

The electric motors 31R, 31L and the mechanical brakes 34R, 34L may bearranged close to each other in a configuration enabling heat transfer,or may be configured as one block.

Incidentally, the power transmission mechanism may be constructed of,for example, a sprocket and a link chain, or may be constructed of aplurality of gears. As another alternative, for example, the electricmotors 31R and 31L may be constructed such that the output shaftsthereof are arranged to oppose the rotating members 27R and 27L so as toarrange the output shafts to be concentric with the rotating members 27Rand 27L, and the output shafts of the electric motors 31R and 31L may beconnected to the rotating members 27R and 27L, respectively, through theintermediary of reducers (e.g., planetary gear devices).

The rotating members 27R and 27L are formed in the same shapes ascircular truncated cones, the diameters of which reduce toward the wheelassembly 5, and the outer peripheral surfaces thereof form tapered outerperipheral surfaces 39R and 39L.

A plurality of the free rollers 29R are arrayed about the tapered outerperipheral surface 39R of the rotating member 27R such that the freerollers 29R are arranged at regular intervals on the circumferenceconcentric with the rotating member 27R. Further, these free rollers 29Rare installed to the tapered outer peripheral surface 39R through theintermediary of the brackets 41R and rotatively supported by thebrackets 41R.

Similarly, a plurality of free rollers 29L (of the same quantity as thatof the free rollers 29R) are arrayed about the tapered outer peripheralsurface 39L of the rotary member 27L such that the free rollers 29L arearrayed at regular intervals on the circumference concentric with therotating member 27L. Further, these free rollers 29L are installed tothe tapered outer peripheral surface 39L through the intermediary of thebrackets 41L and rotatively supported by the brackets 41L.

The wheel assembly 5 is disposed concentrically with the rotatingmembers 27R and 27L, and held between the free rollers 29R adjacent tothe rotating member 27R and the free rollers 29L adjacent to therotating member 27L.

In this case, as illustrated in FIG. 1 and FIG. 5, the free rollers 29Rand 29L are disposed in postures in which the axial centers C3 thereofare inclined against the axial center C2 of the wheel assembly 5 andalso inclined against the diametrical direction of the wheel assembly 5(the radial direction connecting the axial center C2 and the freerollers 29R and 29L when the wheel assembly 5 is observed in thedirection of the axial center C2 thereof). Further, in the aforesaidpostures, the outer peripheral surfaces of the free rollers 29R and 29L,respectively, are pressed into contact aslant with the inner peripheralsurface of the wheel assembly 5.

More generally speaking, the right free rollers 29R are pressed intocontact with the inner peripheral surface of the wheel assembly 5 inpostures in which a frictional force component in the direction aboutthe axial center C2 (a frictional force component in the tangentialdirection of the inner periphery of the wheel assembly 5) and africtional force component in the direction about the center C1 of thecross-section of the wheel assembly 5 (a frictional force component inthe tangential direction of the circular cross section) can be appliedto the wheel assembly 5 at a surface in contact with the wheel assembly5 when the rotating member 27R is rotatively driven about the axialcenter C2. The same applies to the left free rollers 29L.

In this case, as described above, the cover members 21R and 21L arebiased by the springs, which are not shown, in the direction fornarrowing the bottom end portions (the distal ends of the forkedportions) of the cover members 21R and 21L. Thus, the urging force holdsthe wheel assembly 5 between the right free rollers 29R and the leftfree rollers 29L, and the free rollers 29R and 29L are maintained in thepress contact with the wheel assembly 5 (more specifically, the presscontact state that enables a frictional force to act between the freerollers 29R and 29L and the wheel assembly 5).

(Basic Operation of the Vehicle)

In the vehicle 1 having the structure described above, when the rotatingmembers 27R and 27L are rotatively driven at the same velocity in thesame direction by the electric motors 31R and 31L, respectively, thewheel assembly 5 will rotate about the axial center C2 in the samedirection as those of the rotating members 27R and 27L. This causes thewheel assembly 5 to circumrotate on a floor surface in the fore-and-aftdirection and the whole vehicle 1 will travel in the fore-and-aftdirection. In this case, the wheel assembly 5 does not rotate about thecenter C1 of the cross-section thereof.

Further, if, for example, the rotating members 27R and 27L arerotatively driven in opposite directions from each other at velocitiesof the same magnitude, then the wheel assembly 5 will rotate about thecenter C1 of the cross section thereof. This causes the wheel assembly 5to travel in the direction of the axial center C2 thereof (i.e., in thelateral direction), thus causing the whole vehicle 1 to travel in thelateral direction. In this case, the wheel assembly 5 does not rotateabout the axial center C2 thereof.

Further, if the rotating members 27R and 27L are rotatively driven inthe same direction or opposite directions at velocities that aredifferent from each other (velocities including directions), then thewheel assembly 5 will rotate about the axial center C2 and also rotateabout the center C1 of the cross-section thereof.

At this time, motions combining the aforesaid rotational motions(combined motions) cause the wheel assembly 5 to travel in directionsinclined relative to the fore-and-aft direction and the lateraldirection, thus causing the whole vehicle 1 to travel in the samedirection as that of the wheel assembly 5. The traveling direction ofthe wheel assembly 5 in this case will change, depending upon thedifference between the rotational velocities, including the rotationaldirections, of the rotating members 27R and 27L (the rotational velocityvectors, the polarities of which are defined according to rotationaldirections).

The traveling motions of the wheel assembly 5 effected as describedabove. Therefore, by controlling the rotational velocities (includingthe rotational directions) of the electric motors 31R and 31L, andconsequently by controlling the rotational velocities of the rotatingmembers 27R and 27L, it becomes possible to control the moving velocityand the traveling direction of the vehicle 1.

Incidentally, the seat (the payload supporting part) 3 and the base body9 are tiltable about the lateral axial center C2, the axial center C2 ofthe wheel assembly 5 being the supporting point, and also tiltabletogether with the wheel assembly 5 about the longitudinal axis, theground contact surface (the lower end surface) of the wheel assembly 5being the supporting point.

(Construction of the Control Device of the Vehicle)

The construction for controlling the operation of the vehicle 1according to the present embodiment will now be described. In thefollowing description, assuming an XYZ coordinate system, in which thelongitudinal horizontal axis is indicated by an X-axis, the lateralhorizontal axis is indicated by a Y-axis, and the vertical direction isindicated by a Z-axis, as illustrated in FIG. 1 and FIG. 2, thefore-and-aft direction and the lateral direction may be referred to asthe X-axis direction and the Y-axis direction, respectively.

First, the control of the operation of the vehicle 1 will be outlined.According to the present embodiment, basically, if the occupant seatedon the seat 3 tilts his/her upper body (more specifically, if the upperbody is tilted such that the position of the overall center-of-gravitypoint combining the occupant and the vehicle 1 (the position projectedonto a horizontal plane) is moved), then the base body 9 is tiltedtogether with the seat 3 toward the side to which the upper body hasbeen tilted. At this time, the traveling motion of the wheel assembly 5is controlled such that the vehicle 1 travels toward the side to whichthe base body 9 has tilted. For example, if the occupant tilts his/herupper body forward, causing the base body 9 to tilt forward togetherwith the seat 3, then the traveling motion of the wheel assembly 5 iscontrolled to cause the vehicle 1 to travel forward.

In other words, according to the present embodiment, the operation inwhich the occupant moves his/her upper body, causing the seat 3 and thebase body 9 to tilt provides one basic steering operation for thevehicle 1 (a motion request of the vehicle 1), and the traveling motionof the wheel assembly 5 is controlled through the actuator 7 accordingto the steering operation.

Here, in the vehicle 1 according to the present embodiment, the groundcontact surface of the wheel assembly 5 as the ground contact surface ofthe whole vehicle 1 will be a single local region which is smaller thana region resulting from projecting all the vehicle 1 and the occupantthereon onto a floor surface, and a floor reaction force will act onlyon the single local region. For this reason, in order to prevent thebase body 9 from falling due to tilting, the wheel assembly 5 must bemoved such that the overall center-of-gravity point of the occupant andthe vehicle 1 is positioned substantially right above the ground contactsurface of the wheel assembly 5.

Therefore, according to the present embodiment, the posture of the basebody 9 in a state wherein the overall center-of-gravity point of theoccupant and the vehicle 1 is positioned substantially right above thecentral point of the wheel assembly 5 (the central point on the axialcenter C2) (more precisely, in a state wherein the center-of-gravitypoint is positioned substantially right above the ground contact surfaceof the wheel assembly 5) is defined as a desired posture, and basically,the traveling motion of the wheel assembly 5 is controlled such that theactual posture of the base body 9 is converged to the desired posture.

Further, in a state wherein no occupant is aboard the vehicle 1, theposture of the base body 9 in a state which the center-of-gravity pointof the vehicle 1 alone is positioned substantially right above thecentral point of the wheel assembly 5 (the central point on the axialcenter C2) (more precisely, a state wherein the center-of-gravity pointis positioned substantially right above the ground contact surface ofthe wheel assembly 5) is defined as a desired posture, and the actualposture of the base body 9 is converged to the desired posture. Thus,the traveling motion of the wheel assembly 5 is controlled such that thevehicle 1 supports itself without causing the base body 9 to fall fromtilting.

Further, the traveling motion of the wheel assembly 5 is controlled sothat, in either state of the state in which the occupant is aboard thevehicle 1 and in which the occupant is not aboard the vehicle 1, themoving velocity of the vehicle 1 increases as the deviation of theactual posture of the base body 9 from the desired posture increases,and the movement of the vehicle 1 stops in the case where the actualposture of the base body 9 coincides with the desired posture.

Supplementally, “the posture” means a spatial orientation. In thepresent embodiment, when the base body 9 tilts together with the seat 3,the postures of the base body 9 and the seat 3 change. Further, in thepresent embodiment, the base body 9 and the seat 3 integrally tilt, sothat converging the posture of the base body 9 to the desired posture isequivalent to converging the posture of the seat 3 to a desired postureassociated with the seat 3 (the posture of the seat 3 in a state whereinthe posture of the base body 9 coincides with a desired posture of thebase body 9).

According to the present embodiment, in order to control the operationof the vehicle 1 as described above, a control unit 50 constituted of anelectronic circuit unit which mainly includes a microcomputer and adrive circuit unit for the electric motors 31R and 31L, a tilt sensor 52for measuring a tilt angle θb relative to the vertical direction (thegravitational direction) of a predetermined portion of the base body 9and a changing velocity thereof (=dθb/dt), a load sensor 54 fordetecting whether or not an occupant is aboard the vehicle 1, and rotaryencoders 56R and 56L serving as angle sensors for detecting therotational angles and the rotational angular velocities of the outputshafts of the electric motors 31R and 31L, respectively, are mounted atappropriate places of the vehicle 1, as illustrated in FIG. 1 and FIG.2.

In this case, the control unit 50 and the tilt sensor 52 are installedto the support frame 13 by, for example, being accommodated in thesupport frame 13 of the base body 9. Further, the load sensor 54 isincorporated in the seat 3. Further, the rotary encoders 56R and 56L areprovided integrally with the electric motors 31R and 31L. The rotaryencoders 56R and 56L may alternatively be attached to the rotatingmembers 27R and 27L, respectively.

More specifically, the aforesaid tilt sensor 52 is constructed of anacceleration sensor and a rate sensor (angular velocity sensor), such asa gyro sensor, and outputs detection signals of these sensors to thecontrol unit 50. Then, the control unit 50 carries out predeterminedmeasurement arithmetic processing (this may be publicly known arithmeticprocessing) on the basis of the outputs of the acceleration sensor andthe rate sensor of the tilt sensor 52 thereby to calculate the measuredvalue of the tilt angle θb of the portion, to which the tilt sensor 52is installed (the support frame 13 in the present embodiment), relativeto the vertical direction and the measured value of the tilt angularvelocity θbdot, which is a change velocity (differential value) thereof.

In this case, to be more specific, the tilt angle θb to be measured(hereinafter referred to as a base body tilt angle θb in some cases) isconstituted of a component in the direction about the Y-axis (a pitchdirection) θb_x and a component in the direction about the X-axis (aroll direction) θb_y. Similarly, the tilt angular velocity θbdot to bemeasured (hereinafter referred to a base body tilt angular velocityθbdot in some cases) is constituted of a component in the directionabout the Y-axis (the pitch direction) θbdot_x (=dθb_x/dt) and acomponent in the direction about the X-axis (the roll direction)θbdot_y(=dθb_y/dt).

Supplementally, according to the present embodiment, the seat 3 tiltsintegrally with the support frame 13 of the base body 9, so that thebase body tilt angle θb also has a meaning as the tilt angle of thepayload supporting part 3.

In the description of the present embodiment, regarding variables, suchas a motional state amount having components in directions of the X-axisand the Y-axis, such as the aforesaid base body tilt angle θb (ordirections about axes), or variables, such as coefficients related tothe motional state amount, the reference characters of the variableswill be accompanied by a suffix “_x” or “_y” to distinguishably denotethe components.

In this case, for the variables related to translational motions, suchas a translational velocity, a component in the X-axis direction thereofwill be accompanied by the suffix “_x” and a component in the Y-axisdirection thereof will be accompanied by the suffix “_y.”

Meanwhile, regarding the variables related to rotational motions, suchas angles, rotational velocities (angular velocities), and angularacceleration, for the purpose of convenience, a component in thedirection about the Y-axis will be accompanied by the suffix “_x” and acomponent in the direction about the X-axis will be accompanied by thesuffix “_y” in order to match the variables related to translationalmotions with suffixes.

Further, to denote a variable in the form of a pair of a component inthe X-axis direction (or a component in the direction about the Y-axis)and a component in the Y-axis direction (or a component in the directionabout the X-axis), the suffix “_xy” is added to the reference characterof the variable. For example, to express the aforesaid base body tiltangle θb in the form of the pair of a component in the direction aboutthe Y-axis θb_x and a component in the direction about the X-axis θb_y,the pair will be denoted by “the base body tilt angle θb_xy.”

The load sensor 54 is incorporated in the seat 3 so as to be subjectedto a load from the weight of an occupant when the occupant sits on theseat 3, and outputs a detection signal based on the load to the controlunit 50. Then, the control unit 50 determines whether or not theoccupant is aboard the vehicle 1 on the basis of the measured value ofthe load indicated by the output of the load sensor 54.

In place of the load sensor 54, a switch type sensor which, for example,turns on when an occupant sits on the seat 3 may be used.

The rotary encoder 56R generates a pulse signal each time the outputshaft of the electric motor 31R rotates for a predetermined angle, andoutputs the pulse signal to the control unit 50. Then, based on thepulse signal, the control unit 50 measures the rotational angle of theoutput shaft of the electric motor 53R and further measures the temporalchange rate (differential value) of the measured value of the rotationalangle as the rotational angular velocity of the electric motor 53R. Thesame applies to the rotary encoder 56L for the electric motor 31L.

The control unit 50 carries out predetermined arithmetic processing byusing the aforesaid measured values thereby to determine velocitycommands, which are the desired values of the rotational angularvelocities of the electric motors 31R and 31L, respectively, and carriesout feedback control on the rotational angular velocity of each of theelectric motors 31R and 31L according to the determined velocitycommands

Incidentally, the relationship between the rotational angular velocityof the output shaft of the electric motor 31R and the rotational angularvelocity of the rotating member 27R will be a proportional relationshipbased on the speed reduction ratio of a fixed value between the outputshaft and the rotating member 27R. Hence, for the sake of convenience,in the description of the present embodiment, the rotational angularvelocity of the electric motor 31R will mean the rotational angularvelocity of the rotating member 27R. Similarly, the rotational angularvelocity of the electric motor 31L will mean the rotational angularvelocity of the rotating member 27L.

(Outline of the Control Method of the Vehicle)

The following will describe in more detail the control processingcarried out by the control unit 50.

The control unit 50 executes the processing (main routine processing)illustrated by the flowchart of FIG. 6 at a predetermined controlprocessing cycle.

First, in STEP1, the control unit 50 acquires an output of a tilt sensor52.

Subsequently, the control unit 50 proceeds to STEP2 to calculate ameasured value θb_xy_s of a base body tilt angle θb and a measured valueθbdot_xy_s of a base body tilt angular velocity θbdot on the basis ofthe acquired output of the tilt sensor 52.

In the following description, to denote the observed value (the measuredvalue or an estimated value) of an actual value of a variable (a stateamount), such as the measured value θb_xy_s, by a reference character,the reference character of the variable will have a suffix “_s”.

Next, after acquiring an output of a load sensor 54 in STEP3, thecontrol unit 50 carries out the determination processing in STEP4. Inthe determination processing, the control unit 50 determines whether ornot the vehicle 1 has an occupant aboard (whether or not an occupant issitting on the seat 3) by determining whether or not the load measuredvalue indicated by the acquired output of the load sensor 54 is largerthan a predetermined value which has been set beforehand.

Then, if the determination result in STEP4 is affirmative, then thecontrol unit 50 carries out the processing for setting a desired valueθb_xy_obj of the base body tilt angle θb and the processing for settingthe values of constant parameters (e.g., the basic values of variousgains) for controlling the operation of the vehicle 1 in STEP5 andSTEP6, respectively.

In STEP5, the control unit 50 sets a predetermined desired value for aboarding mode as the desired value θb_xy_obj of the base body tilt angleθb.

Here, the term “boarding mode” means the operation mode of the vehicle 1in the case where the occupant is aboard the vehicle 1. The desiredvalue θb_xy_obj for the boarding mode is preset such that desired valueθb_xy_obj coincides or substantially coincides with the measured valueθb_xy_s of the base body tilt angle θb measured on the basis of anoutput of the tilt sensor 52 in a posture of the base body 9 in whichthe overall center-of-gravity point of the vehicle 1 and the occupantseated on the seat 3 (hereinafter referred to as the vehicle-occupantoverall center-of-gravity point) is positioned substantially right abovea ground contact surface of the wheel assembly 5.

Further, in STEP6, the control unit 50 sets predetermined values for theboarding mode as the values of constant parameters for controlling theoperation of the vehicle 1. The constant parameters include, forexample, hx, hy, Ki_a_x, Ki_b_x, Ki_a_y, and Ki_b_y (i=1, 2, 3), whichwill be discussed later.

Meanwhile, if the determination result in STEP4 is negative, then thecontrol unit 50 carries out the processing for setting a desired valueθb_xy_obj of a base body tilt angle θb_xy and the processing for settingthe values of constant parameters for controlling the operation of thevehicle 1 in STEP7 and STEP8, respectively.

In STEP7, the control unit 50 sets a predetermined desired value for anautonomous mode as the desired value θb_xy_obj of the base body tiltangle θb.

Here, the term “autonomous mode” means an operation mode of the vehicle1 in the case where the occupant is not aboard the vehicle 1. Thedesired value θb_xy_obj for the autonomous mode is preset such thatdesired value θb_xy_obj coincides or substantially coincides with themeasured value θb_xy_s of the base body tilt angle θb measured on thebasis of an output of the tilt sensor 52 in a posture of the base body 9in which the center-of-gravity point of the vehicle 1 alone (hereinafterreferred to as the vehicle-alone center-of-gravity point) is positionedsubstantially right above the ground contact surface of the wheelassembly 5. The desired value θb_xy_obj for the autonomous mode isgenerally different from the desired value θb_xy_obj for the boardingmode.

Further, in STEP8, the control unit 50 sets predetermined values for theautonomous mode as the values of constant parameters for controlling theoperation of the vehicle 1. The values of the constant parameters forthe autonomous mode are different from the values of the constantparameters for the boarding mode.

The aforesaid values of the constant parameters are set to be differentbetween the boarding mode and the autonomous mode, because the responsecharacteristics of the operations of the vehicle 1 relative to controlinputs are different from each other due to the differences in theheight of the aforesaid center-of-gravity point, the overall mass, andthe like between the respective modes.

By the processing in STEP4 to STEP8 described above, the desired valueθb_xy_obj of the base body tilt angle θb_xy and the values of theconstant parameters are set for each of the operational modes, namely,the boarding mode and the autonomous mode.

Incidentally, the processing in STEP5 and STEP6 or the processing inSTEP7 and STEP8 is not essential to carry out for each controlprocessing cycle. Alternatively, the processing may be carried out onlywhen the determination result in STEP4 changes.

Supplementally, in both the boarding mode and the autonomous mode, thedesired value of a component θbdot_x in the direction about a Y-axis ofthe base body tilt angular velocity θbdot and the desired value of acomponent θbdot_y in the direction about an X-axis thereof are bothzero. For this reason, it is unnecessary to carry out the processing forsetting a desired value of the base body tilt angular velocity θbdot_xy.

After carrying out the processing in STEP5 and STEP6 or the processingin STEP7 and STEP8 as described above, the control unit 50 carries outvehicle control arithmetic processing in STEP9 thereby to determine thespeed commands for electric motors 31R and 31L, respectively. Thevehicle control arithmetic processing will be discussed later in detail.

Subsequently, the control unit 50 proceeds to STEP10 to carry out theprocessing for controlling the operations of the electric motors 31R and31L according to the speed commands determined in STEP9. In thisoperation control processing, based on the difference between the speedcommand for the electric motor 31R determined in STEP9 and the measuredvalue of the rotational speed of the electric motor 31R measured on thebasis of an output of a rotary encoder 56R, the control unit 50determines a desired value (desired torque) of an output torque of theelectric motor 31R such that the difference is converged to zero. Then,the control unit 50 controls the current supplied to the electric motor31R such that the electric motor 31R outputs an output torque of thedesired torque. The same applies to the operation control of the leftelectric motor 31L.

The above has described the general control processing carried out bythe control unit 50.

(Details of the Control Method of the Vehicle)

The vehicle control arithmetic processing in STEP9 mentioned above willnow be described in detail.

In the following description, the vehicle-occupant overallcenter-of-gravity point in the boarding mode and the vehicle-alonecenter-of-gravity point in the autonomous mode will be genericallyreferred to as the vehicle system center-of-gravity point. The vehiclesystem center-of-gravity point will mean the vehicle-occupant overallcenter-of-gravity point when the operational mode of the vehicle 1 isthe boarding mode and will mean the vehicle-alone center-of-gravitypoint when the operational mode of the vehicle 1 is the autonomous mode.

Further, in the following description, regarding the values (updatedvalues) determined at each control processing cycle by the control unit50, a value determined at a current (latest) control processing cyclemay be referred to as a current value, and a value determined at animmediately preceding control processing cycle may be referred to as aprevious value. Further, a value will mean a current value unlessotherwise specified as a current value or a previous value.

Further, regarding the velocity and acceleration in the X-axisdirection, a forward-facing direction will be defined as a positivedirection, and regarding the velocity and acceleration in the Y-axisdirection, a left-facing direction will be defined as the positivedirection.

In the present embodiment, the vehicle control arithmetic processing inSTEP9 is carried out, assuming that the dynamic behaviors of the vehiclesystem center-of-gravity point (more specifically, the behaviorsobserved by projecting the behaviors from the Y-axis direction onto aplane (XZ plane) which is orthogonal thereto, and the behaviors observedby projecting the behaviors from the X-axis direction onto a plane (YZplane) which is orthogonal thereto) are approximately expressed by thebehaviors of an inverted pendulum model (dynamic behaviors of theinverted pendulum), as shown in FIG. 7.

In FIG. 7, unparenthesized reference numerals denote the referencenumerals associated with the inverted pendulum model observed from theY-axis direction, while the parenthesized reference numerals denote thereference numerals associated with the inverted pendulum model observedfrom the X-axis direction.

In this case, the inverted pendulum model expressing a behavior observedfrom the Y-axis direction is provided with a mass point 60_x positionedat the vehicle system center-of-gravity point and a imaginary wheel62_x, which has a rotational axis 62 a_x parallel to the Y-axisdirection and which freely circumrotate on a floor surface (hereinafterreferred to as the imaginary wheel 62_x). Further, the mass point 60_xis supported by a rotational shaft 62 a_x of the imaginary wheel 62_xthrough the intermediary of a linear rod 64_x such that the mass point60_x is swingable about the rotational shaft 62 a_x, using therotational shaft 62 a_x as the supporting point.

In this inverted pendulum model, a motion of the mass point 60_xcorresponds to a motion of the vehicle system center-of-gravity pointobserved from the Y-axis direction. Further, it is assumed that the tiltangle θbe_x of the rod 64_x relative to a vertical direction coincideswith a difference θbe_x_s between a base body tilt angle measured valueθb_x_s in the direction about the Y-axis and a base body tilt angledesired value θb_x_obj (=θb_x_s−θb_x_obj). It is also assumed that achanging velocity of the tilt angle θbe_x of the rod 64_x (=dθbe_x/dt)coincides with a base body tilt angular velocity measured valueθbdot_x_s in the direction about the Y-axis. Further, it is assumed thata moving velocity Vw_x of the imaginary wheel 62_x (the translationalmoving velocity in the X-axis direction) coincides with the movingvelocity of the wheel assembly 5 of the vehicle 1 in the X-axisdirection.

Similarly, the inverted pendulum model expressing a behavior observedfrom the X-axis direction (refer to the parenthesized reference numeralsin FIG. 7) is provided with a mass point 60_y positioned at the vehiclesystem center-of-gravity point and a imaginary wheel 62_y, which has arotational axis 62 a_y parallel to the X-axis direction and which freelycircumrotate on a floor surface (hereinafter referred to as theimaginary wheel 62_y). Further, the mass point 60_y is supported by arotational shaft 62 a_y of the imaginary wheel 62_y through theintermediary of a linear rod 64_y such that the mass point 60_y isswingable about the rotational shaft 62 a_y, using the rotational shaft62 a_y as the supporting point.

In this inverted pendulum model, a motion of the mass point 60_ycorresponds to a motion of the vehicle system center-of-gravity pointobserved from the X-axis direction. Further, it is assumed that the tiltangle θbe_y of the rod 64_y relative to the vertical direction coincideswith a difference θbe_y_s between a base body tilt angle measured valueθb_y_s in the direction about the X-axis and a base body tilt angledesired value θb_y_obj (=θb_y_s−θb_y_obj). It is also assumed that achanging velocity of the tilt angle θbe_y of the rod 64_y (=dθbe_y/dt)coincides with a base body tilt angular velocity measured valueθbdot_y_s in the direction about the X-axis. Further, it is assumed thata moving velocity Vw_y of the imaginary wheel 62_y (the translationalmoving velocity in the Y-axis direction) coincides with the movingvelocity of the wheel assembly 5 of the vehicle 1 in the Y-axisdirection.

It is assumed that the imaginary wheels 62_x and 62_y have radii Rw_xand Rw_y of predetermined values, respectively.

It is assumed that relationships represented by expressions 01a and 01bgiven below hold between rotational angular velocities ωw_x and ωw_y ofthe imaginary wheels 62_x and 62_y, respectively, and rotational angularvelocities ω_R and ω_L of the electric motors 31R and 31L, respectively(more accurately, the rotational angular velocities ω_R and ω_L ofrotational members 27R and 27L, respectively).ωw _(—) x=(ω_(—) R+ω _(—) L)/2  Expression 01aωw _(—) y=C·(ω_(—) R−ω _(—) L)/2  Expression 01b

Where “C” in expression 01b denotes a coefficient of a predeterminedvalue that depends on a mechanical relationship or slippage between freerollers 29R and 29L and the wheel assembly 5. The positive directions ofωw_x, ω_R and ω_L are the rotational directions in which the imaginarywheel 62_x rotates in the case where the imaginary wheel 62_xcircumrotates forward. The positive direction of ωw_y is the rotationaldirection in which the imaginary wheel 62_y rotates in the case wherethe imaginary wheel 62_y circumrotates leftwards.

Here, the dynamics of the inverted pendulum model shown in FIG. 7 isrepresented by expressions 03x and 03y given below. Expression 03x is anexpression that represents the dynamics of the inverted pendulum modelobserved from the Y-axis direction, while expression 03y is anexpression that represents the dynamics of the inverted pendulum modelobserved from the X-axis direction.d ² θbe _(—) x/dt ²=α_(—) x·θbe _(—) x+β _(—) x·ωwdot _(—) x  Expression03xd ² θbe _(—) y/dt ²=α_(—) y·θbe _(—) y+β _(—) y·ωwdot _(—) y  Expression03y

Where ωwdot_x in expression 03x denotes the rotational angularacceleration (first-order differential value of the rotational angularvelocity ωw_x) of the imaginary wheel 62_x, α_x denotes a coefficientwhich depends on a mass or a height h_x of the mass point 60_x, and β_xdenotes a coefficient which depends on an inertia (inertial moment) orthe radius Rw_x of the imaginary wheel 62_x. The same applies toωwdot_y, α_y, and β_y in expression 03y.

As may be understood from these expressions 03x and 03y, the motions ofthe mass points 60_x and 60_y of the inverted pendulum model (i.e., themotions of the vehicle system center-of-gravity point) are specified,depending on the rotational angular acceleration ωwdot_x of theimaginary wheel 62_x and the rotational angular acceleration ωwdot_y ofthe imaginary wheel 62_y, respectively.

In the present embodiment, therefore, the rotational angularacceleration ωwdot_x of the imaginary wheel 62_x is used as themanipulated variable (control input) for controlling the motion of thevehicle system center-of-gravity point observed from the Y-axisdirection, while the rotational angular acceleration ωwdot_y of theimaginary wheel 62_y is used as the manipulated variable (control input)for controlling the motion of the vehicle system center-of-gravity pointobserved from the X-axis direction.

To briefly describe the vehicle control arithmetic processing in STEP9,the control unit 50 determines imaginary wheel rotational angularacceleration commands ωwdot_x_cmd and ωwdot_y_cmd, which are the commandvalues (desired values) of the rotational angular accelerations ωwdot_xand ωwdot_y as the manipulated variables such that the motion of themass point 60_x observed in the X-axis direction and the motion of themass point 60_y observed in the Y-axis direction become the motionscorresponding to desired motions of the vehicle system center-of-gravitypoint. Further, the control unit 50 determines the values obtained byintegrating the imaginary wheel rotational angular acceleration commandsωwdot_x_cmd and ωwdot_y_cmd, respectively, as the imaginary wheelrotational angular velocity commands ωw_x_cmd and ωw_y_cmd, which arethe command values (desired values) of the rotational angular velocitiesωw_x and ωw_y of the imaginary wheels 62_x and 62_y, respectively.

Further, the control unit 50 defines the moving velocity of theimaginary wheel 62_x corresponding to the imaginary wheel rotationalangular velocity command ωw_x_cmd (=Rw_x·ωw_x_cmd) and the movingvelocity of the imaginary wheel 62_y corresponding to the imaginarywheel rotational angular velocity command ωw_y_cmd (=Rw_y·ωw_y_cmd) asthe desired moving velocity of the wheel assembly 5 of the vehicle 1 inthe X-axis direction and the desired moving velocity thereof in theY-axis direction, respectively, and the control unit 50 determinesvelocity commands ω_R_cmd and ω_L_cmd of the electric motors 31R and31L, respectively, so as to achieve the desired moving velocities.

In the present embodiment, the imaginary wheel rotational angularacceleration commands ωwdot_x_cmd and ωwdot_y_cmd as the manipulatedvariables (control inputs) are determined by adding up three manipulatedvariable components, as indicated by expressions 07x and 07y, which willbe discussed later.

Supplementally, of the imaginary wheel rotational angular accelerationcommands ωwdot_x_cmd and ωwdot_y_cmd as the manipulated variable(control input) in the present embodiment, ωwdot_x_cmd is a rotationalangular acceleration of the imaginary wheel 62_x moving in the X-axisdirection, so that it functions as the manipulated variable whichstipulates the driving force to be imparted to the wheel assembly 5 soas to make the wheel assembly 5 move in the X-axis direction. Further,because ωwdot_y_cmd is a rotational angular acceleration of theimaginary wheel 62_y moving in the Y-axis direction, so that itfunctions as the manipulated variable which stipulates the driving forceto be imparted to the wheel assembly 5 so as to make the wheel assembly5 move in the Y-axis direction.

The control unit 50 is provided with the functions illustrated in theblock diagram of FIG. 8 as the functions for carrying out the vehiclecontrol arithmetic processing in STEP9 as described above.

More specifically, the control unit 50 is provided with an errorcalculator 70 which calculates the base body tilt angle error measuredvalue θbe_xy_s, which is the difference between the base body tilt anglemeasured value θb_xy_s and the base body tilt angle desired valueθb_xy_obj, a center-of-gravity velocity calculator 72 which calculatesan estimated center-of-gravity velocity value Vb_xy_s as an observedvalue of a center-of-gravity velocity Vb_xy, which is the movingvelocity of the vehicle system center-of-gravity point, acenter-of-gravity velocity restrictor 76 which determines a desiredcenter-of-gravity velocity for control Vb_xy_mdfd as the desired valueof the center-of-gravity velocity Vb_xy by taking into account arestriction based on a permissible range of the rotational angularvelocities of the electric motors 31R and 31L, and a gain adjustor 78which determines a gain adjustment parameter Kr_xy for adjusting thevalues of the gain coefficients of expressions 07x and 07y, which willbe discussed later.

The control unit 50 is further provided with a posture controlcalculator 80 which calculates the imaginary wheel rotational angularvelocity command ωw_xy_cmd, and a motor command calculator 82 whichconverts the imaginary wheel rotational angular velocity commandωw_xy_cmd into a pair of a velocity command ω_R_cmd (a command value ofa rotational angular velocity) for the right electric motor 31R and avelocity command ω_L_cmd (a command value of a rotational angularvelocity) for the left electric motor 31L.

Reference numeral 84 in FIG. 8 denotes a delay element which receivesthe imaginary wheel rotational angular velocity command ωw_xy_cmdcalculated at each control processing cycle by the posture controlcalculator 80. The delay element 84 outputs a previous value ωw_xy_cmd_pof the imaginary wheel rotational angular velocity command ωw_xy_cmd ateach control processing cycle.

In the vehicle control arithmetic processing in STEP9 described above,the processing by the aforesaid processing sections is carried out asdescribed below.

The control unit 50 first carries out the processing by the errorcalculator 70 and the processing by the center-of-gravity velocitycalculator 72.

The error calculator 70 receives the base body tilt angle measuredvalues θb_xy_s (θb_x_s and θb_y_s) calculated in the aforesaid STEP2 andthe desired values θb_xy_obj (θb_x_obj and θb_y_obj) set in theaforesaid STEP5 or STEP7. Then, the error calculator 70 subtractsθb_x_obj from θb_x_s to calculate the base body tilt angle errormeasured value θbe_x_s (=θb_x_s−θb_x_obj) in the direction about theY-axis, and also subtracts θb_y_obj from θb_y_s to calculate the basebody tilt angle error measured value θbe_y_s (=θb_y_s−θb_y_obj) in thedirection about the X-axis.

The processing by the error calculator 70 may be carried out before thevehicle control arithmetic processing in STEP9. For example, theprocessing by the error calculator 70 may be carried out during theprocessing in the aforesaid STEP5 or STEP7.

The center-of-gravity velocity calculator 72 is input with the currentvalue of the base body tilt angular velocity measured value θbdot_xy_s(θbdot_x_s and θbdot_y_s) calculated in STEP2, and also a previous valueωw_xy_cmd_p (ωw_x_cmd_p and ωw_y_cmd_p) of a imaginary wheel velocitycommand ωw_xy_cmd is input from a delay element 84. Thereafter, thecenter-of-gravity velocity calculator 72 calculates from these inputvalues an estimated center-of-gravity velocity value Vb_xy_s (Vb_x_s andVb_y_s), according to a predetermined arithmetic expression on the basisof the above-mentioned inverted pendulum model.

Specifically, the center-of-gravity velocity calculator 72 calculatesVb_x_s and Vb_y_s, respectively, from expressions 05x, 05y below.Vb _(—) x _(—) s=Rw _(—) x·ωw _(—) x_cmd_(—) p+h_x·θbdot_(—) x _(—)s  05xVb _(—) y _(—) s=Rw _(—) y·ωw _(—) y _(—) cmd _(—) p+h_y·θbdot_(—)y_s  05y

In the expressions 05x, 05y, Rw_x, Rw_y are respective radius of theimaginary wheel 62_x, 62_y as is explained above, and these values arepredetermined values set beforehand. Further, h_x, h_y are respectiveheight of the mass point 60_x, 60_y of the inverted pendulum model. Inthe present embodiment, the height of the vehicle systemcenter-of-gravity point is to be maintained substantially constant.Therefore, as the values of h_x, h_y, predetermined values set beforehand are used. Supplementally, height h_x, h_y are included in theconstant parameter, the value of which is set in STEP 6 or STEP8.

The first term in the right side of the equation 05x is a movingvelocity of the imaginary wheel 62_x in the X-axis directioncorresponding to the previous value ωw_x_cmd_p of the velocity commandof the imaginary wheel 62_x, and this moving velocity corresponds to thecurrent value of the actual moving velocity of the wheel assembly 5 inthe X-axis direction. Further, the second term in the right side of theequation 05x corresponds to the current value of the moving velocity ofthe vehicle system center-of-gravity point in the X-axis directionarising from the base body 9 tilting at the tilt angular velocity ofθbdot_x_s about the Y-axis direction (relative moving velocity withrespect to the wheel assembly 5). The same applies to equation 05y.

Here, a pair of the measured value (current value) of the rotationalangular velocity of the electric motors 31R, 31L, respectively, that aremeasured on the basis of the outputs from the rotary encoders 56R, 56L,may be converted to a pair of the rotational angular velocity of theimaginary wheels 62_x, 62_y, respectively, and these rotational angularvelocities may be used instead of ωw_x_cmd_p, ωw_y_cmd_p in equations05x, 05y. However, in eliminating the influence of the noise included inthe measured value of the rotational angular velocity, it isadvantageous to use ωw_x_cmd_p, ωw_y_cmd_p which are desired values.

Subsequently, the control unit 50 carries out the processing by thecenter-of-gravity velocity restrictor 76 and the processing by the gainadjustor 78. In this case, the center-of-gravity velocity restrictor 76and the gain adjustor 78 respectively receive the estimatedcenter-of-gravity velocity values Vb_xy_s (Vb_x_s and Vb_y_s) calculatedby the center-of-gravity velocity calculator 72 as described above.

Further, the gain adjustor 78 determines the gain adjustment parametersKr_xy (Kr_x and Kr_y) on the basis of the input estimatedcenter-of-gravity velocity values Vb_xy_s (Vb_x_s and Vb_y_s).

The processing by the gain adjustor 78 will be described below withreference to FIG. 9 and FIG. 10.

As illustrated in FIG. 9, the gain adjustor 78 supplies the inputestimated center-of-gravity velocity values Vb_x_s and Vb_y_s to alimiting processor 86. The limiting processor 86 adds, as appropriate,restrictions based on the permissible ranges of the rotational angularvelocities of the electric motors 31R and 31L to the estimatedcenter-of-gravity velocity values Vb_x_s and Vb_y_s, thereby generatingoutput values Vw_x_lim1 and Vw_y_lim1. The output value Vw_x_lim1 meansa value obtained after limiting the moving velocity Vw_x of theimaginary wheel 62_x in the X-axis direction and the output valueVw_y_lim1 means a value obtained after limiting the moving velocity Vw_yof the imaginary wheel 62_y in the Y-axis direction.

The processing by the limiting processor 86 will be described in furtherdetail with reference to FIG. 10. The parenthesized reference charactersin FIG. 10 denote the processing by a limiting processor 104 of thecenter-of-gravity velocity restrictor 76, which will be discussed later,and may be ignored in the description related to the processing by thelimiting processor 86.

The limiting processor 86 first supplies the estimated center-of-gravityvelocity values Vb_x_s and Vb_y_s to processors 86 a_x and 86 a_y,respectively. The processor 86 a_x divides Vb_x_s by the radius Rw_x ofthe imaginary wheel 62_x to calculate the rotational angular velocityωw_x_s of the imaginary wheel 62_x in the case where it is assumed thatthe moving velocity of the imaginary wheel 62_x in the X-axis directioncoincides with Vb_x_s. Similarly, the processor 86 a_y calculates therotational angular velocity ωw_y_s of the imaginary wheel 62_y(=Vb_y_s/Rw_y) in the case where it is assumed that the moving velocityof the imaginary wheel 62_y in the Y-axis direction coincides withVb_y_s.

Subsequently, the limiting processor 86 converts the pair of ωw_x_s andωw_y_s into a pair of the rotational angular velocity ω_R_s of theelectric motor 31R and the rotational angular velocity ω_L_s of theelectric motor 31L by an XY-RL converter 86 b.

According to the present embodiment, the conversion is implemented bysolving a simultaneous equation obtained by replacing ωw_x, ωw_y, ω_Rand ω_L of the aforesaid expressions 01a and 01b by ωw_x_s, ωw_y_s,ω_R_s and ω_L_s, respectively, taking the ω_R_s and ω_L_s as unknowns.

Subsequently, the limit processor 86 supplies the output values ω_R_sand ω_L_s of the XY-RL converter 86 b to limiters 86 c_R and 86 c_L,respectively. At this time, the limiter 86 c_R directly outputs theω_R_s as an output value ω_R_lim1 if the ω_R_s falls within thepermissible range for the right motor, which has an upper limit value(>0) and a lower limit value (<0) of predetermined values setbeforehand. If the ω_R_s deviates from the permissible range for theright motor, then the limiter 86 c_R outputs, as the output valueω_R_lim1, a boundary value of the upper limit value or the lower limitvalue of the permissible range for the right motor whichever is closerto the ω_R_s. Thus, the output value ω_R_lim1 of the limiter 86 c_R islimited to a value within the permissible range for the right motor.

Similarly, the limiter 86 c_L directly outputs the ω_L_s as an outputvalue ω_L_lim1 if the ω_L_s falls within the permissible range for theleft motor, which has an upper limit value (>0) and a lower limit value(<0) of predetermined values set beforehand. If the ω_L_s deviates fromthe permissible range for the left motor, then the limiter 86 c_Loutputs, as the output value ω_L_lim1, a boundary value of the upperlimit value or the lower limit value of the permissible range for theleft motor whichever is closer to the ω_L_s. Thus, the output valueω_L_lim1 of the limiter 86 c_L is limited to a value within thepermissible range for the left motor.

The permissible range for the right motor described above is apermissible range which has been set so as to prevent the rotationalangular velocity (absolute value) of the right electric motor 31R frombecoming excessively high thereby to prevent the maximum value of thetorque that can be output by the electric motor 31R from decreasing.This applies also to the permissible range for the left motor.

Subsequently, the limit processor 86 converts the pair of the outputvalues ω_R_lim1 and ω_L_lim1 of the limiters 86 c_R and 86 c_L,respectively, into a pair of the rotational angular velocities ωw_x_lim1and ωw_y_lim1 of the imaginary wheels 62_x and 62_y, respectively, by anRL-XY converter 86 d.

The conversion is the processing of the inverse conversion of theprocessing of the conversion by the aforesaid XY-RL converter 86 b. Thisprocessing is implemented by solving a simultaneous equation obtained byreplacing ωw_x, ωw_y, ω_R and ω_L of the aforesaid expressions 01a and01b by ωw_x_lim1, ωw_y_lim1, ω_R_lim1 and ω_L_lim1, respectively, takingthe ωw_x_lim1 and ωw_y_lim1 as unknowns.

Subsequently, the limit processor 86 supplies the output valuesωw_x_lim1 and ωw_y_lim1 of the RL-XY converter 86 d to processors 86 e_xand 86 e_y, respectively. The processor 86 e_x multiplies ωw_x_lim1 bythe radius Rw_x of the imaginary wheel 62_x to convert ωw_x_lim1 intothe moving velocity Vw_x_lim1 of the imaginary wheel 62_x. In the samemanner, the processor 86 e_y converts ωw_y_lim1 into the moving velocityVw_y_lim1 of the imaginary wheel 62_y (=ωw_y_lim1·Rw_y).

If it is assumed that the processing by the limiting processor 86described above causes the moving velocity Vw_x of the imaginary wheel62_x in the X-axis direction and the moving velocity Vw_y of theimaginary wheel 62_y in the Y-axis direction to agree with the estimatedcenter-of-gravity velocity values Vb_x_s and Vb_y_s, respectively (inother words, if it is assumed that the moving velocity of the wheelassembly 5 in the X-axis direction and the moving velocity in the Y-axisdirection are set to agree with Vb_x_s and Vb_y_s, respectively), thenthe pair of output values Vw_x_lim1 and Vw_y_lim1 coinciding with Vb_x_sand Vb_y_s, respectively, is output from the limiting processor 86 ifthe rotational angular velocities ω_R_s and ω_L_s of the electric motors31R and 31L, respectively, which are required for achieving the movingvelocities, both fall within permissible ranges.

Meanwhile, if both or one of the rotational angular velocities ω_R_s andω_L_s of the electric motors 31R and 31L, respectively, deviates fromthe permissible range or ranges, then both or one of the rotationalangular velocities is forcibly limited to be within the permissiblerange, and a pair of the moving velocities in the X-axis direction andthe Y-axis direction Vw_x_lim1 and Vw_y_lim1 corresponding to a pair ofthe limited rotational angular velocities ω_R_lim1 and ω_L_lim1 of theelectric motors 31R and 31L, respectively, is output from the limitingprocessor 86.

Hence, the limiting processor 86 generates a pair of output valuesVw_x_lim1 and Vw_y_lim1 such that the output values Vw_x_lim1 andVw_y_lim1 agree with Vb_x_s and Vb_y_s, respectively, as much aspossible under an essential required condition that the rotationalangular velocities of the electric motors 31R and 31L corresponding tothe pair of the output values Vw_x_lim1 and Vw_y_lim1, respectively, donot deviate from the permissible ranges.

Referring back to the description of FIG. 9, the gain adjustor 78 thencarries out the processing by calculators 88_x and 88_y. The calculator88_x receives the estimated center-of-gravity velocity value in theX-axis direction Vb_x_s and the output value Vw_x_lim1 of the limitingprocessor 86. Then, the calculator 88_x calculates a value Vover_xobtained by subtracting Vb_x_s from Vw_x_lim1 and outputs the valueVover_x. Further, the calculator 88_y receives the estimatedcenter-of-gravity velocity value in the Y-axis direction Vb_y_s and theoutput value Vw_y_lim1 of the limiting processor 86. Then, thecalculator 88_y calculates a value Vover_y obtained by subtractingVb_y_s from Vw_y_lim1 and outputs the value Vover_y.

In this case, if the output values Vw_x_lim1 and Vw_y_lim1 are notforcibly restricted by the limiting processor 86, then Vw_x_lim1=Vb_x_sand Vw_(—y)_lim1=Vb_y_s. Therefore, the output values Vover_x andVover_y of the calculators 88_x and 88_y, respectively, will be bothzero.

Meanwhile, if the output values Vw_x_lim1 and Vw_y_lim1 of the limitingprocessor 86 are generated by forcibly restricting the input valuesVb_x_s and Vb_y_s, then a corrected amount from Vb_x_s of Vw_x_lim1(=Vw_x_lim1−Vb_x_s) and a corrected amount from Vb_y_s of Vw_(y)_lim1(=Vw_y_lim1−Vb_y_s) will be output from the calculators 88_x and 88_y,respectively.

Subsequently, the gain adjustor 78 passes the output value Vover_x ofthe calculator 88_x through processors 90_x and 92_x in this orderthereby to determine the gain adjustment parameter Kr_x. Further, thegain adjustor 78 passes the output value Vover_y of the calculator 88_ythrough processors 90_y and 92_y in this order thereby to determine thegain adjustment parameter Kr_y. The gain adjustment parameters Kr_x andKr_y both take values within the range from 0 to 1.

The processor 90_x calculates and outputs the absolute value of theinput Vover_x. Further, the processor 92_x generates Kr_x such that theoutput value Kr_x monotonously increases relative to an input value|Vover_x| and has a saturation characteristic. The saturationcharacteristic is a characteristic in which a change amount of an outputvalue relative to an increase in an input value becomes zero orapproaches to zero when the input value increases to a certain level.

In this case, according to the present embodiment, if the input value|Vover_x| is a preset, predetermined value or less, then the processor92_x outputs, as Kr_x, a value obtained by multiplying the input value|Vover_x| by a proportionality coefficient of a predetermined value.Further, if the input value |Vover_x| is larger than the predeterminedvalue, then the processor 92_x outputs 1 as Kr_x. Incidentally, theproportionality coefficient is set such that the product of |Vover_x|and the proportionality coefficient becomes 1 when |Vover_x| agrees witha predetermined value.

The processing by processors 90_y and 92_y is the same as that carriedout by the processors 90_x and 92_x, respectively, described above.

If the output values Vw_x_lim1 and Vw_y_lim1 in the limiting processor86 are not forcibly restricted by the processing carried out by the gainadjustor 78 described above, that is, if the rotational angularvelocities of the electric motors 31R and 31L fall within thepermissible ranges even when the electric motors 31R and 31L areoperated such that the moving velocities Vw_x and Vw_y of the wheelassembly 5 in the X-axis direction and the Y-axis direction,respectively, agree with the estimated center-of-gravity velocity valuesVb_x_s and Vb_y_s, respectively, then the gain adjustment parametersKr_x and Kr_y are both determined to be zero. Therefore, normally,Kr_x=Kr_y=0.

Meanwhile, if the output values Vw_x_lim1 and Vw_y_lim1 of the limitingprocessor 86 are generated by forcibly restricting the input valuesVb_x_s and Vb_y_s, that is, if the rotational angular velocity of one ofthe electric motors 31R and 31L deviates from the permissible range (ifthe absolute value of one of the rotational angular velocities becomesexcessively high) when the electric motors 31R and 31L are operated suchthat the moving velocities Vw_x and Vw_y of the wheel assembly 5 in theX-axis direction and the Y-axis direction, respectively, agree with theestimated center-of-gravity velocity values Vb_x_s and Vb_y_s, then thevalues of the gain adjustment parameters Kr_x and Kr_y are determined onthe basis of the absolute values of the aforesaid corrected amountsVover_x and Vover_y, respectively. In this case, Kr_x is determined tobe a larger value as the absolute value of the corrected amount Vover_xincreases, the upper limit value thereof being 1. The same applies toKr_y.

The center-of-gravity velocity restrictor 76 determines the desiredcenter-of-gravity velocities for control Vb_xy_mdfd (Vb_x_mdfd andVb_y_mdfd), by executing the process shown in the block diagram of FIG.11, using the input estimated center-of-gravity velocity values Vb_xy_s(Vb_x_s and Vb_y_s).

To be more specific, the center-of-gravity velocity restrictor 76 firstcarries out the processing by stead-state error calculators 94_x and94_y.

In this case, the stead-state error calculator 94_x receives theestimated center-of-gravity velocity value in the X-axis directionVb_x_s and also receives the previous value Vb_x_mdfd_p of the desiredcenter-of-gravity velocity for control in the X-axis direction Vb_x_mdfdthrough the intermediary of a delay element 96_x. Then, in thestead-state error calculator 94_x, first, the input Vb_x_s is suppliedto a proportional-differential compensation component (PD compensationcomponent) 94 a_x. The proportional-differential compensation component94 a_x is a compensation component whose transfer function is denoted by1+Kd·S, and adds the input Vb_x_s and the value obtained by multiplyingthe differential value thereof (temporal change rate) by a coefficientKd of a predetermined value, and outputs the value resulting from theaddition.

Subsequently, the stead-state error calculator 94_x calculates, by acalculator 94 b_x, the value obtained by subtracting the inputVb_x_mdfd_p from the output value of the proportional-differentialcompensation component 94 a_x, then supplies the output value of thecalculator 94 b_x to a low-pass filter 94 c_x having a phasecompensation function. The low-pass filter 94 c_x is a filter whosetransfer function is denoted by (1+T2·S)/(1+T1·S). Then, the stead-stateerror calculator 94_x outputs the output value Vb_x_prd of the low-passfilter 94 c_x.

Further, the stead-state error calculator 94_y receives the estimatedcenter-of-gravity velocity value in the Y-axis direction Vb_y_s and alsoreceives the previous value Vb_y_mdfd_p of the desired center-of-gravityvelocity for control in the Y-axis direction Vb_y_mdfd through theintermediary of a delay element 96_y.

Then, as with the stead-state error calculator 94_x described above, thestead-state error calculator 94_y carries out the processing by aproportional-differential compensation component 94 a_y, a calculator 94b_y, and a low-pass filter 94 c_y in order and outputs an output valueVb_y_prd of the low-pass filter 94 c_y.

Here, the output value Vb_x_prd of the stead-state error calculator 94_xhas a meaning as a stead-state error of a future estimatedcenter-of-gravity velocity value in the X-axis direction presumed from acurrent motion state of the vehicle system center-of-gravity pointobserved from the Y-axis direction (in other words, the motion state ofthe mass point 60_x of the inverted pendulum model observed from theY-axis direction) relative to the desired center-of-gravity velocity forcontrol Vb_x_mdfd of an expected convergence value. Similarly, theoutput value Vb_y_prd of the stead-state error calculator 94_y has ameaning as a stead-state error of a future estimated center-of-gravityvelocity value in the Y-axis direction presumed from a current motionstate of the vehicle system center-of-gravity point observed from theX-axis direction (in other words, the motion state of the mass point60_y of the inverted pendulum model observed from the X-axis direction)relative to the desired center-of-gravity velocity for control Vb_y_mdfdof an expected convergence value. Hereinafter, the output valuesVb_x_prd and Vb_y_prd of the stead-state error calculators 94_x and94_y, respectively, will be referred to as the predictedcenter-of-gravity velocity stead-state error values.

After executing the process of the stead-state error calculators 94_xand 94_y as explained above, the center-of-gravity velocity restrictor76 inputs the predicted center-of-gravity velocity stead-state errorvalues Vb_x_prd and Vb_y_prd, respectively, to a limiting processor 100.The processing by the limiting processor 100 is the same as theprocessing by the limiting processor 86 of the gain adjustor 78described above. In this case, as indicated by the parenthesizedreference characters in FIG. 10, only the input values and the outputvalues of the individual processing sections of the limiting processor100 are different from those of the limiting processor 86.

To be more specific, in the limiting processor 100, rotational angularvelocities ωw_x_t and ωw_y_t of the imaginary wheels 62_x and 62_y inthe case where it is assumed that the moving velocities Vw_x and Vw_y ofthe imaginary wheels 62_x and 62_y, respectively, coincide with Vb_x_prdand Vb_y_prd, respectively, are calculated by the processors 86 a_x and86 a_y, respectively. Then, the pair of the rotational angularvelocities ωw_x_t and ωw_y_t is converted into the pair of therotational angular velocities ω_R_t and ω_L_t of the electric motors 31Rand 31L by the XY-RL converter 86 b.

Further, these rotational angular velocities ω_R_t and ω_L_t are limitedto values within the permissible range for the right motor and thepermissible range for the left motor, respectively, by limiters 86 c_Rand 86 c_L. Then, the values ω_R_lim2 and ω_L_lim2, which have beensubjected to the limitation processing, are converted by the RL-XYconverter 86 d into the rotational angular velocities ωw_x_lim2 andωw_y_lim2 of the imaginary wheels 62_x and 62_y.

Subsequently, the moving velocities Vw_x_lim2 and Vw_y_lim2 of theimaginary wheels 62_x and 62_y corresponding to the rotational angularvelocities ωw_x_lim2 and ωw_y_lim2 are calculated by the processors 86e_x and 86 e_y, respectively, and these moving velocities Vw_x_lim2 andVw_y_lim2 are output from the limiting processor 100.

By carrying out the processing by the limiting processor 100 describedabove, the limiting processor 100 generates a pair of output valuesVw_x_lim2 and Vw_y_lim2 such that the output values Vw_x_lim2 andVw_y_lim2 agree with Vb_x_t and Vb_y_t, respectively, as much aspossible under an essential required condition that the rotationalangular velocities of the electric motors 31R and 31L corresponding tothe pair of the output values Vw_x_lim2 and Vw_y_lim2, respectively, donot deviate from the permissible ranges, as with the limiting processor86.

Incidentally, the permissible ranges for the right motor and left motorin the limiting processor 100 do not have to be the same as thepermissible ranges in the limiting processor 86, and may be set to bepermissible ranges that are different from each other.

Referring back to the description of FIG. 11, the center-of-gravityvelocity restrictor 76 then carries out the processing by calculators102_x and 102_y to calculate the desired center-of-gravity velocitiesfor control Vb_x_mdfd and Vb_y_mdfd, respectively. In this case, thecalculator 102_x calculates a value, which is obtained by subtractingthe predicted center-of-gravity velocity stead-state error value in theX-axis direction Vb_x_prd from the output value Vw_x_lim2 of thelimiting processor 100, as the desired center-of-gravity velocity forcontrol in the X-axis direction Vb_x_mdfd. Similarly, the calculator102_y calculates a value, which is obtained by subtracting the predictedcenter-of-gravity velocity stead-state error value in the Y-axisdirection Vb_y_prd from the output value Vw_y_lim2 of the limitingprocessor 100, as the desired center-of-gravity velocity for control inthe Y-axis direction Vb_y_mdfd.

Regarding the desired center-of-gravity velocities for control Vb_x_mdfdand Vb_y_mdfd determined as described above, in the case where theoutput values Vw_x_lim2 and Vw_y_lim2 are not forcibly restricted by thelimiting processor 100, that is, in the case where the rotationalangular velocities of the electric motors 31R and 31L fall within thepermissible ranges even when the electric motors 31R and 31L areoperated such that the moving velocities of the wheel assembly 5 in theX-axis direction and the Y-axis direction, respectively, agree with thepredicted center-of-gravity velocity stead-state error values Vb_x_prdand Vb_y_prd, respectively, the desired center-of-gravity velocities forcontrol Vb_x_mdfd and Vb_y_mdfd are both determined to be “0”.Therefore, normally, Vb_x_mdfd=Vb_y_mdfd=0.

Meanwhile, if the output values Vw_x_lim2 and Vw_y_lim2 of the limitingprocessor 100 are generated by forcibly restricting the input valuesVb_x_t and Vb_y_t, that is, if the rotational angular velocity of one ofthe electric motors 31R and 31L deviates from the permissible range (ifthe absolute value of one of the rotational angular velocities becomesexcessively high) when the electric motors 31R and 31L are operated suchthat the moving velocities of the wheel assembly 5 in the X-axisdirection and the Y-axis direction, respectively, agree with thepredicted center-of-gravity velocity stead-state error values Vb_x_prdand Vb_y_prd, then for the X-axis direction, a correction amount fromthe input value Vb_x_prd of the output value Vw_x_lim2 of the limitingprocessor 100 (=Vw_x_lim2−Vb_x_prd) is determined as the desiredcenter-of-gravity velocity for control Vb_x_mdfd in the X-axisdirection.

Further, regarding the Y-axis direction, a correction amount from theinput value Vb_y_prd of the output value Vw_y_lim2 of the limitingprocessor 100 (=Vw_y_lim2−Vb_y_prd) is determined as the desiredcenter-of-gravity velocity for control Vb_y_mdfd in the Y-axisdirection.

In this case, for example with respect to the velocity in the X-axisdirection, the desired center-of-gravity velocity for control Vb_x_mdfdbecomes the velocity in opposite direction from the predictedcenter-of-gravity velocity stead-state error value Vb_x_prd in theX-axis direction which is output from the stead-state error calculator94_x. The same applies to the velocity in the Y-axis direction.

The above has described the processing by the center-of-gravity velocityrestrictor 76.

Returning to the description of FIG. 8, after carrying out theprocessing by the center-of-gravity velocity restrictor 76, the gainadjustor 78, and the error calculator 70 as described above, the controlunit 50 carries out the processing by the posture control calculator 80.

The processing by the posture control calculator 80 will be describedbelow by referring to FIG. 12. Incidentally, the unparenthesizedreference characters in FIG. 12 are the reference characters related tothe processing for determining the aforesaid imaginary wheel rotationalangular velocity command ωw_x_cmd, which is the desired value of therotational angular velocity of the imaginary wheel 62_x circumrotatingin the X-axis direction. The parenthesized reference characters are thereference characters related to the processing for determining theaforesaid imaginary wheel rotational angular velocity command ωw_y_cmd,which is the desired value of the rotational angular velocity of theimaginary wheel 62_y circumrotating in the Y-axis direction.

The posture control calculator 80 receives the base body tilt angleerror measured value θbe_xy_s calculated by the error calculator 70, thebase body tilt angular velocity measured values θbdot_xy_s calculated inthe aforesaid STEP2, the estimated center-of-gravity velocity valuesVb_xy_s calculated by the center-of-gravity velocity calculator 72, thedesired center-of-gravity velocities for control Vb_xy_mdfd calculatedby the center-of-gravity velocity restrictor 76, and the gain adjustmentparameters Kr_xy calculated by the gain adjustor 78.

Then, the posture control calculator 80 first calculates the imaginarywheel rotational angular acceleration commands ωwdot_xy_cmd according tothe following expressions 07x and 07y by using the above receivedvalues.ωwdot_(—) x_cmd=K1_(—) x·θbe _(—) x _(—) s+K2_(—) x·θbdot_(—) x _(—)s+K3_(—) x·(Vb _(—) x _(—) s−Vb _(—) x_mdfd)  Expression 07xωwdot_(—) y_cmd=K1_(—) y·θbe _(—) y _(—) s+K2_(—) y·θbdot_(—) y _(—)s+K3_(—) y·(Vb _(—) y _(—) s−Vb _(—) y_mdfd)  Expression 07y

Hence, according to the present embodiment, the imaginary wheelrotational angular acceleration command ωwdot_x_cmd denoting themanipulated variable (control input) for controlling the motion of themass point 60_x of the inverted pendulum model observed from the Y-axisdirection (i.e., the motion of the vehicle system center-of-gravitypoint observed from the Y-axis direction), and the imaginary wheelrotational angular acceleration command ωwdot_y_cmd denoting themanipulated variable (control input) for controlling the motion of themass point 60_y of the inverted pendulum model observed from the X-axisdirection (i.e., the motion of the vehicle system center-of-gravitypoint observed from the X-axis direction) are determined by adding upthree manipulated variable components (the three terms of the right sideof each of expressions 07x and 07y).

The gain coefficients K1_x, K1_y in these expressions 07x, 07y arefeedback gains related to the tilt angle of the base body 9 (or the seat3), the gain coefficients K2_x, K2_y are feedback gains related to thetilt angular velocity (temporal change rate) of the base body 9 (or theseat 3), and the gain coefficients K3_x, K3_y are feedback gains relatedto the moving velocity of the vehicle system center-of-gravity point (apredetermined representative point of the vehicle 1).

In this case, the gain coefficients K1_x, K2_x, and K3_x related to themanipulated variable components in expression 07x are variably set onthe basis of the gain adjustment parameter Kr_x, while the gaincoefficients K1_y, K2_y, and K3_y related to the manipulated variablecomponents in expression 07y are variably set on the basis of the gainadjustment parameter Kr_y. Hereinafter, the gain coefficients K1_x,K2_x, and K3_x in expression 07x may be referred to as the first gaincoefficient K1_x, the second gain coefficient K2_x, and the third gaincoefficient K3_x, respectively. The same applies to the gaincoefficients K1_y, K2_y, and K3_y in expression 07y.

An i-th gain coefficient Ki_x (i=1, 2, or 3) in expression 07x and ani-th gain coefficient Ki_y (i=1, 2, or 3) in expression 07y aredetermined on the basis of the gain adjustment parameters Kr_x and Kr_yaccording to expressions 09x and 09y given below, as indicated by thenote in FIG. 12.Ki _(—) x=(1−Kr _(—) x)·Ki _(—) a _(—) x+Kr _(—) x·Ki _(—) b _(—)x  Expression 09xKi _(—) y=(1−Kr _(—) y)·Ki _(—) a _(—) y+Kr _(—) y·Ki _(—) b _(—)y  Expression 09y

-   -   (i=1, 2, 3)

Here, Ki_a_x and Ki_b_x in expression 09x denote constant values setbeforehand as the gain coefficient values on a minimum end (an end closeto zero) of the i-th gain coefficient Ki_x and as the gain coefficientvalue on a maximum end (an end away from zero), respectively. The sameapplies to Ki_a_y and Ki_b_y in expression 09y.

Thus, each i-th gain coefficient Ki_x (i=1, 2 or 3) used in thecalculation of expression 07x is determined as a weighed mean value ofthe constant values Ki_a_x and Ki_b_x corresponding thereto. Further, inthis case, the weight applied to each of Ki_a_x and Ki_b_x is changedaccording to the gain adjustment parameter Kr_x. Therefore, if Kr_x=0,then Ki_x=Ki_a_x, and if Kr_x=1, then Ki_x=Ki_b_x. As Kr_x approaches 1from 0, the i-th gain coefficient Ki_x approaches Ki_b_x from Ki_a_x.

Similarly, each i-th gain coefficient Ki_y (i=1, 2 or 3) used in thecalculation of expression 07y is determined as a weighed mean value ofthe constant values Ki_a_y and Ki_b_y corresponding thereto. Further, inthis case, the weight applied to each of Ki_a_y and Ki_b_y is changedaccording to the gain adjustment parameter Kr_y. Therefore, as with thecase of Ki_x, as the value of Kr_y changes from 0 to 1, the value of thei-th gain coefficient Ki_y changes between Ki_a_y and Ki_b_y.

As is explained above, Kr_x and Kr_y are normally (to be more specific,in the case where the output values Vw_x_lim1 and Vw_y_lim1 are notforcibly restricted at the limit processor 86 of the gain adjustor 78),“0”. Therefore, the i-th gain coefficient Ki_x and Ki_y (i=1, 2 or 3)normally become Ki_x=Ki_a_x and Ki_y=Ki_a_y, respectively.

Supplementally, the aforesaid constant values Ki_a_x, Ki_b_x and Ki_a_y,Ki_b_y (i=1, 2 or 3) are included in the constant parameters, the valuesof which are set in the aforesaid STEP6 or STEP8.

The posture control calculator 80 uses the first to the third gaincoefficients K1_x, K2_x, and K3_x determined as described above toperform the calculation of the above expression 07x, thereby calculatingthe imaginary wheel rotational angular acceleration command ωwdot_x_cmdrelated to the imaginary wheel 62_x circumrotating in the X-axisdirection.

More detailedly, referring to FIG. 12, the posture control calculator 80calculates a manipulated variable component u1_x obtained by multiplyingthe base body tilt angle error measured value θbe_x_s by the first gaincoefficient K1_x and a manipulated variable component u2_x obtained bymultiplying the base body tilt angular velocity measured value θbdot_x_sby the second gain coefficient K2_x by processors 80 a and 80 b,respectively. Further, the posture control calculator 80 calculates thedifference between the estimated center-of-gravity velocity value Vb_x_sand the desired center-of-gravity velocity for control Vb_x_mdfd(=Vb_x_s−Vb_x_mdfd) by a calculator 80 d, and calculates, by a processor80 c, a manipulated variable component u3_x obtained by multiplying thecalculated difference by the third gain coefficient K3_x. Then, theposture control calculator 80 adds up these manipulated variablecomponents u1_x, u2_x, and u3_x by a calculator 80 e so as to calculatethe imaginary wheel rotational angular acceleration command ωwdot_x_cmd.

Similarly, the posture control calculator 80 carries out the calculationof the above expression 07y by using the first to the third gaincoefficients K1_y, K2_y, and K3_y determined as described above, therebycalculating the imaginary wheel rotational angular acceleration commandωwdot_y_cmd related to the imaginary wheel 62_y circumrotating in theY-axis direction.

In this case, the posture control calculator 80 calculates a manipulatedvariable component u1_y obtained by multiplying the base body tilt angleerror measured value θbe_y_s by the first gain coefficient K1_y and amanipulated variable component u2_y obtained by multiplying the basebody tilt angular velocity measured value θbdot_y_s by the second gaincoefficient K2_y by the processors 80 a and 80 b, respectively. Further,the posture control calculator 80 calculates the difference between theestimated center-of-gravity velocity value Vb_y_s and the desiredcenter-of-gravity velocity for control Vb_y_mdfd (=Vb_y_s−Vb_y_mdfd) bythe calculator 80 d, and calculates, by the processor 80 c, amanipulated variable component u3_y obtained by multiplying thecalculated difference by the third gain coefficient K3_y. Then, theposture control calculator 80 adds up these manipulated variablecomponents u1_y, u2_y, and u3_y by the calculator 80 e so as tocalculate the imaginary wheel rotational angular acceleration commandωwdot_y_cmd.

Here, the first term (=the first manipulated variable component u1_x)and the second term (=the second manipulated variable component u2_x) ofthe right side of expression 07x mean the feedback manipulated variablecomponents for converging the base body tilt angle error measured valueθbe_x_s in the direction about the X-axis to zero (converging the basebody tilt angle measured value θb_x_s to the desired value θb_x_obj) bythe PD law (proportional-differential law) serving as the feedbackcontrol law.

Further, the third term (=the third manipulated variable component u3_x)of the right side of expression 07x means a feedback manipulatedvariable component for converging the difference between the estimatedcenter-of-gravity velocity value Vb_x_s and the desiredcenter-of-gravity velocity for control Vb_x_mdfd to zero (convergingVb_x_s to Vb_x_mdfd) by a proportional law serving as the feedbackcontrol law.

The same applies to the first to the third terms (the first to the thirdmanipulated variable components u1_y, u2_y, and u3_y) of the right sideof expression 07y.

As is explained above, normally (to be more specific, in the case wherethe output values V_x_lim2 and V_y_lim2 are not forcibly limited at thelimit processor 100 of the center-of-gravity velocity restrictor 76),the desired center-of-gravity velocities for control Vb_x_mdfd andVb_y_mdfd are “0”. And, in the normal case where Vb_x_mdfd=Vb_y_mdfd=0,the third manipulated variable components u3_x and u3_y, respectively,coincide with the value obtained by multiplying the third gaincoefficients K3_x and K3_y with the estimated center-of-gravity velocityvalues Vb_x_s and Vb_y_s, respectively.

After calculating the imaginary wheel rotational angular accelerationcommands ωwdot_x_cmd and ωwdot_y_cmd as described above, the posturecontrol calculator 80 integrates these ωwdot_x_cmd and ωwdot_y_cmd by anintegrator 80 f thereby to determine the aforesaid imaginary wheelrotational velocity commands ωw_x_cmd and ωw_y_cmd.

The above has described the details of the processing by the posturecontrol calculator 80.

Supplementally, the imaginary wheel rotational angular accelerationcommand ωwdot_x_cmd may alternatively be calculated by an expressionwherein the third term of the right side of expression 07x is separatedinto the manipulated variable component based on Vb_x_s (=K3_x·Vb_x_s)and the manipulated variable component based on Vb_x_mdfd(=−K3_x·Vb_x_mdfd). Similarly, the imaginary wheel rotational angularacceleration command ωwdot_y_cmd may alternatively be calculated by anexpression wherein the third term of the right side of expression 07y isseparated into the manipulated variable component based on Vb_y_s(=K3_y·Vb_y_s) and the manipulated variable component based on Vb_y_mdfd(=−K3_y·Vb_y_mdfd).

Further, in the present embodiment, the rotational angular accelerationcommands ωdotw_x_cmd and ωdotw_y_cmd of the imaginary wheels 62_x and62_y have been used as the manipulated variables (control inputs) forcontrolling the behaviors of the vehicle system center-of-gravity point.However, for example, the drive torques of the imaginary wheels 62_x and62_y or the translational forces obtained by dividing the drivingtorques by the radii Rw_x and Rw_y of the imaginary wheels 62_x and 62_y(i.e., the frictional forces between the imaginary wheels 62_x, 62_y anda floor surface) may be used as the manipulated variables.

Returning to the description of FIG. 8, the control unit 50 thensupplies the imaginary wheel rotational velocity commands ωw_x_cmd andωw_y_cmd determined as described above by the posture control calculator80 to the motor command calculator 82, and carries out the processing bythe motor command calculator 82 so as to determine a velocity commandω_R_cmd of the electric motor 31R and a velocity command ω_L_cmd of theelectric motor 31L. The processing by the motor command calculator 82 isthe same as the processing by the XY-RL converter 86 b of the aforesaidlimiting processor 86 (refer to FIG. 10).

To be more specific, the motor command calculator 82 determines thevelocity commands ω_R_cmd and ω_L_cmd of the electric motors 31R and 31Lby a simultaneous equation obtained by replacing ωw_x, ωw_y, ω_R and ω_Lof the aforesaid expressions 01a and 01b by ωw_x_cmd, ωw_y_cmd, ω_R_cmdand ω_L_cmd, respectively, taking the ω_R_cmd and ω_L_cmd as unknowns.

Thus, the vehicle control arithmetic processing in the aforesaid STEP9is completed.

(Operation of the Vehicle)

By the control arithmetic processing carried out by the control unit 50as described above, the imaginary wheel rotational angular accelerationcommands ωwdot_xy_cmd denoting the manipulated variables (controlinputs) are determined such that, basically, in the case where theposture of the seat 3 and the base body 9 is maintained at a posture inwhich the aforesaid base body tilt angle error measured values θbe_x_sand θbe_y_s are both zero (hereinafter, this posture will be referred toas the basic posture) even in a motion mode which is either the boardingmode or the autonomous mode, the vehicle system center-of-gravity pointbecomes static. Thereafter, when the posture of the seat 3 and the basebody 9 is tilted with respect to the basic posture, that is, when thehorizontal direction position of the vehicle system center-of-gravitypoint (the vehicle-occupant overall center-of-gravity point or thevehicle-alone center-of-gravity point) is displaced from the state inwhich the same is positioned substantially above the ground contactsurface of the wheel assembly 5, the imaginary wheel rotational angularacceleration commands ωwdot_xy_cmd are determined so as to restore theposture of the seat 3 and the base body 9 to the basic posture (so as tobring θbe_x_s and θbe_y_s close to “0”, or to maintain the same at “0”).

Then, the rotational angular velocities of the electric motors 31R and31L, respectively, obtained by converting the imaginary wheel rotationalangular velocity commands ωw_xy_cmd, which is obtained by integratingeach component of ωwdot_xy_cmd, are determined as the velocity commandsω_R_cmd and ω_L_cmd of the electric motors 31R and 31L. Further, therotational velocities of the electric motors 31R and 31L are controlledaccording to the velocity commands ω_R_cmd and ω_L_cmd. Thus, the movingvelocities of the wheel assembly 5 in the X-axis direction and theY-axis direction, respectively, are controlled so as to agree with themoving velocity of the imaginary wheel 62_x corresponding to ωw_x_cmdand the moving velocity of the imaginary wheel 62_y corresponding toωw_y_cmd, respectively.

With this arrangement, if, for example, the actual base body tilt angleθb_x deviates from the desired value θb_x_obj in the direction about theY-axis by leaning forward, then the wheel assembly 5 moves forward toeliminate the deviation (to converge θbe_x_s to zero). Similarly, if theactual base body tilt angle θb_x deviates from the desired valueθb_x_obj by leaning backward, then the wheel assembly 5 moves backwardto eliminate the deviation (to converge θbe_x_s to zero).

Further, for example, if the actual base body tilt angle θb_y deviatesfrom the desired value θb_y_obj in the direction about the X-axis byleaning rightward, then the wheel assembly 5 moves rightward toeliminate the deviation (to converge θbe_y_s to zero). Similarly, if theactual base body tilt angle θb_y deviates from the desired valueθb_y_obj by leaning leftward, then the wheel assembly 5 moves leftwardto eliminate the deviation (to converge θbe_y_s to zero).

Further, if both the actual base body tilt angles θb_x and θb_y deviatefrom the desired values θb_x_obj and θb_y_obj, respectively, then themoving operation of the wheel assembly 5 in the fore-and-aft directionto eliminate the deviation of θb_x and the moving operation of the wheelassembly 5 in the lateral direction to eliminate the deviation of θb_yare combined, so that the wheel assembly 5 will move in a directioncombining the X-axis direction and the Y-axis direction (a direction atan angle to both the X-axis direction and the Y-axis direction).

Thus, if the posture of the seat 3 and the base body 9 tilts from thebasic posture, then the wheel assembly 5 moves toward the tilting side.Hence, if, for example, the occupant intentionally inclines his/herupper body together with the seat 3 and the base body 9 in the aforesaidboarding mode, then the wheel assembly 5 will move to the tilting side.In the present embodiment, in the case where the seat 3 and the basebody 9 are tilted from the basic posture, the traveling direction of thevehicle system center-of-gravity point within the horizontal surface(traveling direction in the direction orthogonal to the Z-axis) and thetraveling direction of the wheel assembly 5 does not necessarilycoincide, from the reasons to be given later.

When the posture of the seat 3 and the base body 9 is held in a constantposture tilted from the basic posture (a posture in which the base bodytilt angle error measured value θbe_xy_s becomes constant), duringtraveling of the wheel assembly 5 (during traveling of the overallvehicle 1), the moving velocity of the vehicle system center-of-gravitypoint (and consequently the moving velocity of the wheel assembly 5)converges to a moving velocity having a constant error with the desiredcenter-of-gravity velocities for control Vb_xy_mdfd and also the errorthereof depending on the base body tilt angle error measured valueθbe_xy_s.

In the present embodiment, in the normal case where the traveling motionof the wheel assembly 5 is carried out in a moving velocity in which therotational angular velocity of the electric motors 31R and 31L does notbecome too fast (to be more precise, in the case where the output valuesVw_x_lim2 and Vw_y_lim2 are not forcibly restricted by the limitprocessor 100 of the center-of-gravity velocity restrictor 76), thedesired center-of-gravity velocities for control Vb_x_mdfd and Vb_y_mdfdare both maintained at “0”. Thereafter, when the posture of the seat 3and the base body 9 are held in a constant position tilted from thebasic position, in the situation where Vb_x_mdfd and Vb_y_mdfd aremaintained constant, the moving velocity of the vehicle systemcenter-of-gravity point (and consequently the moving velocity of thewheel assembly 5) converges to the moving velocity having the magnitudeand orientation depending on the base body tilt angle error measuredvalue θbe_xy_s.

To give more detailed explanation on the operation mentioned above, in astationary state in which both of the base body tilt angle errormeasured values θbe_x_s and θbe_y_s are held constant, the secondmanipulated variable components u2_x and u2_y becomes “0”. Therefore,the imaginary wheel rotational angular acceleration command ωwdot_x_cmdbecomes a value in which the first manipulated variable component u1_xis added with the third manipulated variable component u3_x, and theimaginary wheel rotational angular acceleration command ωwdot_y_cmdbecomes a value in which the first manipulated variable component u1_yis added with the third manipulated variable component u3_y.

Further, in the stationary state mentioned above, the imaginary wheelrotational angular acceleration commands ωwdot_x_cmd and ωwdot_y_cmdconverge to values in which the moving velocity of the wheel assembly 5may be kept constant. Consequently, the center-of-gravity velocitiesVb_x and Vb_y converge to constant values.

In this case, the second term in the right side of the equation 07x(=u2_x) becomes “0”, the first term on the right side(=u1_x=K1_x*θbe_x_s) becomes a constant value, and the ωwdot_x_cmd onthe left side becomes a constant value, so that a converging value ofthe center-of-gravity velocity Vb_x in the X-axis direction (aconverging value of the estimated center-of-gravity velocity valueVb_x_s, hereinafter referred to as a stationary-state convergingvelocity Vb_x_stb) depends on the base body tilt angle error measuredvalue θbe_x_s about the Y-axis direction. More specifically, Vb_x_stbbecomes Vb_x_stb=(−K1_x*Δθbe_x_s+ωwdot_x_cmd)/K3_x+Vb_x_mdfd, so that itbecomes a function value which monotonously change with respect toθbe_x_s.

Similarly, the second term in the right side of the equation 07y (=u2_y)becomes “0”, the first term on the right side (=u1_y=K1_y*θbe_y_s)becomes a constant value, and ωwdot_y_cmd in the left side becomes aconstant value, so that a converging value of the center-of-gravityvelocity Vb_y in the Y-axis direction (a converging value of theestimated center-of-gravity velocity value Vb_y_s, hereinafter referredto as the stationary-state converging velocity Vb_y_stb) depends on thebase body tilt angle error measured value θbe_y_s about the X-axisdirection. More specifically, Vb_x_stb becomesVb_y_stb=(−K1_y*Δθbe_y_s+ωwdot_y_cmd)/K3_y+Vb_y_mdfd, so that it becomesa function value which monotonously change with respect to θbe_y_s.

As seen from above, when the posture of the seat 3 and the base body 9are kept in a constant posture tilted from the base body in thesituation where the Vb_x_mdfd and Vb_y_mdfd are kept constant, themoving velocity of the vehicle system center-of-gravity point (andconsequently the moving velocity of the wheel assembly 5) converges to amoving velocity with magnitude and orientation depending on the basebody tilt angle error measured value θbe_xy_s.

Further, for example, in the situation where the tilt amount of the basebody 9 and the seat 3 from the basic posture (the base body tilt angleerror measured values θbe_x_s and θbe_y_s) becomes relatively large, andthe moving velocities of the wheel assembly 5 in one or both of theX-axis direction and the Y-axis direction in the case where the tiltamount is maintained stable (these moving velocities correspond to thepredicted center-of-gravity velocity stead-state error values Vb_x_prdand Vb_y_prd, respectively, shown in FIG. 11) becomes excessive movingvelocity so as to make one or both of the rotational angular velocitiesof the electric motors 31R and 31L deviate from the allowable range atthe limiting processor 100, then the velocities in the directionopposite to the moving velocity of the wheel assembly 5 (morespecifically, Vw_x_lim2−Vb_x_prd and Vw_y_lim2−Vb_y_prd) are determinedas the desired center-of-gravity velocities for control Vb_x_mdfd andVb_y_mdfd. Thereafter, of the manipulated variable componentsconstituting the control input, the third manipulated variablecomponents u3_x and u3_y are determined so as to converge the estimatedcenter-of-gravity velocity values Vb_x_s and Vb_y_s to the desiredcenter-of-gravity velocities for control Vb_x_mdfd and Vb_y_mdfd,respectively. By doing so, velocity increasing of the wheel assembly 5is suppressed, and consequently one or both of the rotational angularvelocities of the electric motors 31R and 31L are prevented from beingtoo fast.

Further, in the situation where one or both of the estimatedcenter-of-gravity velocity values Vb_x_s and Vb_y_s become large, andconsequently one or both of the moving velocities of the wheel assembly5 in the X-axis direction and the Y-axis direction become excessivemoving velocity so as to make one or both of the rotational angularvelocities of the electric motors 31R and 31L deviate from the allowablerange at the limiting processor 86, then in the gain adjustor 78, one orboth of the gain adjustment parameters Kr_x and Kr_y are brought closefrom 0 to 1, as the deviation becomes more apparent (more specifically,as the absolute values of the Vover_x and Vover_y shown in FIG. 9 becomelarger).

In this case, each i-th gain coefficient Ki_x (i=1, 2, 3) calculated bythe equation 09x approaches from the constant number Ki_a_x on theminimum side to the constant number Ki_b_x on the maximum side, as Kr_xapproaches to 1. This applies to each i-th gain coefficient Ki_y (i=1,2, 3) calculated by the equation 09y.

Thereafter, by increasing the absolute value of the above-mentioned gaincoefficient, the sensitivity towards the manipulated amount (theimaginary wheel rotational angular acceleration commands ωwdot_x_cmd andωwdot_y_cmd) with respect to the change in the tilt of the base body 9and the seat 3 (the change in the base body tilt angle error measuredvalue θbe_xy_s), and the change in the estimated center-of-gravityvelocity values Vb_xy_s increase. Therefore, when the tilt amount of thebase body 9 and the seat 3 from the basic posture tends to increase, orthe magnitude of the estimated center-of-gravity velocity values Vb_xy_stend to increase, the moving velocity of the wheel assembly 5 iscontrolled so as to promptly dissolve the same. Therefore, it becomespossible to strongly restrict the base body 9 from tilting greatly fromthe basic position or the estimated center-of-gravity velocity valuesVb_xy_s from increasing, and consequently, it becomes possible torestrict one or both of the moving velocity of the wheel assembly 5 inthe X-axis direction and the Y-axis direction becomes excessive velocityso as to make one or both of the rotational angular velocities of theelectric motors 31R and 31L from deviating from the allowable range atthe limiting processor 86.

(Control Method of the Functional Unit)

A control method of the operating mode of the electric motors 31R, 31Lby the control unit 50 will be explained with reference to FIG. 13.

On the basis of output signals from an ammeter (not shown) provided toan electric wire connected to a terminal of a battery (for example ananode terminal), the control unit 50 calculates a measured value of abattery current Ibatt (FIG. 13/STEP 102). The battery current Ibatt isdefined to a “positive” value at the time of charging the battery.

On the basis of output signals from a temperature sensor (not shown)arranged to come into contact with or be in the vicinity of the electricmotors 31R, 31L, respectively, the control unit 50 calculates measuredvalues of the temperatures Tmot_R, Tmot_L of the electric motors 31R,31L, respectively (FIG. 13/STEP 102).

In addition, the measured values of the temperatures Tmot_R, Tmot_L ofthe electric motors 31R, 31L may be calculated by inputting temperatureclimb rates Tmotdot_R, Tmotdot_L of the electric motors 31R, 31L to anintegral component.

The temperature climb rates Tmotdot_R, Tmotdot_L of the electric motors31R, 31L are calculated on the basis of heat generation amounts Qmot_R,Qmot_L and heat discharge amounts Qmot_out_R, Qmot_out_L of the electricmotors 31R, 31L, and heat capacities Cmot_R, Cmot_L of the electricmotors 31R, 31L, and according to equations 11a, 11b.Tmotdot_(—) R=(Qmot_(—) R−Qmot_out_(—) R)/Cmot_(—) R  equation 11aTmotdot_(—) L=(Qmot_(—) L−Qmot_out_(—) L)/Cmot_(—) L  equation 11b

The heat generation amounts Qmot_R, Qmot_L of the electric motors 31R,31L are calculated on the basis of motor currents Imot_R, Imot_L flowingin the electric motors 31R, 31L, and according to equations 12a, 12b.The motor currents Imot_R, Imot_L mean a square root of a sum of asquare of a field current and a square of a torque current. ReferencesrR, rL represent an internal resistance of the electric motors 31R, 31L.Qmot_(—) R=rR(Imot_(—) R)²  equation 12aQmot_(—) L=rL(Imot_(—) L)²  equation 12b

The motor currents Imot_R, Imot_L of the electric motors 31R, 31L arecalculated by the control unit 50 on the basis of output signals from acurrent sensor (not shown) for measuring the current supplied to theelectric motors 31R, 31L.

The heat discharge amounts Qmot_out_R, Qmot_out_L of the electric motors31R, 31L are calculated on the basis of the temperatures Tmot_R, Tmot_Lof the electric motors 31R, 31L and an outside temperature Tat, and aheat transfer coefficient κ between the electric motors 31R, 31L and itsoutside, and according to equations 13a, 13b.Qmot_out_(—) R=κ(Tmot_(—) R−Tat)  equation 13aQmot_out_(—) L=κ(Tmot_(—) L−Tat)  equation 13b

On the measured values of the temperatures Tmot_R, Tmot_L of theelectric motors 31R, 31L and temperature threshold values Tmot_th_R,Tmot_th_L of the electric motors 31R, 31L stored in a memory, adifference between temperature allowances Tmot_suff_R, Tmot_suff_L ofthe electric motors 31R, 31L is calculated as a motor temperatureallowance deviation Tmot_suff_diff (FIG. 13/STEP 104).

The temperature allowances Tmot_suff_R, Tmot_suff_L of the electricmotors 31R, 31L are represented as differences Tmot_th_R−Tmot_R,Tmot_th_L−Tmot_L, in the state where the temperatures Tmot_R, Tmot_L areequal to or less than the temperature threshold values Tmot_th_R,Tmot_th_L. The temperature threshold values Tmot_th_R, Tmot_th_L are setfrom the viewpoint that there is a possibility of significantlyshortening a heat deterioration lifetime of the electric motors 31R,31L, in the case where the temperatures Tmot_R, Tmot_L of the electricmotors 31R, 31L exceed the temperature threshold values Tmot_th_R,Tmot_th_L. The motor temperature allowance deviation Tmot_suff_diff isrepresented by an equation 14.Tmot_suff_diff=Tmot_suff_(—) L−Tmot_suff_(—) R=(Tmot_(—) th _(—)L−Tmot_(—) L)−(Tmot_(—) th _(—) R−Tmot_(—) R)  equation 14

In the case where the specification and configuration of the electricmotors 31R, 31L are equal, and the temperature threshold valuesTmot_th_R and T mot_th_L are equal, the temperature differenceTmot_R−Tmot_L of the electric motors 31R, 31L is calculated as the motortemperature allowance deviation Tmot_suff_diff, as is apparent from theequation 14.

In addition, a sum of the difference between the temperature allowancesTmot_suff_R, Tmot_suff_L of the electric motors 31R, 31L(Tmot_suff_dot_L−Tmot_suff_dot_R) and a proportional value α of thetemporal change rate of the difference (α is a positive coefficient) maybe calculated as the motor temperature allowance deviationTmot_suff_diff.

It is determined whether or not a state of charge (charge statequantity) SOC of the battery is equal to or more than a charge thresholdvalue SOCth (FIG. 13/STEP 106). The state of charge SOC of the batterymay be calculated as a time integral value of a result of inputting thebattery current Ibatt to a calculator taking an integral component as atransfer function. The charge threshold value SOCth is set from theviewpoint that the possibility of promoting degradation of the batteryperformance becomes higher in the case where the state of charge SOC ofthe battery greatly exceeds the charge threshold value SOCth, and isstored in a memory.

In the case where it is determined that the state of charge SOC of thebattery is equal to or more than the charge threshold value SOCth (FIG.13/STEP 106 . . . YES), the control unit 50 sets a motor heat generationratio r (FIG. 13/STEP 108).

More specifically, a ratio of the heat generation amount Qmot_R of theelectric motor 31R to a total heat generation amount Qmot of theelectric motors 31R, 31L is set as the motor heat generation ratio r.For example, the motor heat generation ratio r is set according to aheat generation ratio function as a dependent variable taking thetemperature allowance deviation Tmot_suff_diff as a main variable, whichis represented by a curve, for example, as is shown in FIG. 14.

The heat generation ratio function is set to a value of “0.5”, in thecase where the temperature allowance deviation Tmot_suff_diff is zero,i.e., in the case where the temperature allowance Tmot_suff_R of theright electric motor 31R is equal to the temperature allowanceTmot_suff_L of the left electric motor 31L. In the case where the heatcapacity Cmot_R of the right electric motor 31R is different from theheat capacity Cmot_L of the left electric motor 31L, then this valuebecomes “Cmot_R/(Cmot_R+Cmot_L)”, and not 0.5.

Further, the heat generation ratio function has a characteristics ofapproaching “1” continuously or discontinuously as the absolute value ofthe temperature allowance deviation Tmot_suff_diff becomes larger, inthe case where the temperature allowance deviation Tmot_suff_diff isnegative, i.e., in the case where the temperature allowance Tmot_suff_Rof the right electric motor 31R is larger than the temperature allowanceTmot_suff_L of the left electric motor 31L.

Still further, the heat generation ratio function has a characteristicsof approaching “0” continuously or discontinuously as the absolute valueof the temperature allowance deviation Tmot_suff_diff becomes larger, inthe case where the temperature allowance deviation Tmot_suff_diff ispositive, i.e., in the case where the temperature allowance Tmot_suff_Lof the left electric motor 31L is larger than the temperature allowanceTmot_suff_R of the right electric motor 31R.

In the case where the temperature allowance deviation Tmot_suff_diff isnegative, the heat generation ratio function shows a characteristics ofapproaching rapidly to “1” or taking a large value, as the batterycurrent Ibatt is lower. In the case where the temperature allowancedeviation Tmot_suff_diff is positive, the heat generation ratio functionshows a characteristics of approaching rapidly to “0” or taking a smallvalue, as the battery current Ibatt is lower. In addition, the changingmode of the heat generation ratio function may be constant regardless ofthe battery current Ibatt.

A current desired total heat generation amount Qmot_obj of the electricmotors 31R, 31L is set as a sum of a previous desired total heatgeneration amount Qmot_obj_p and a proportional value K·Ibatt of thebattery current Ibatt (K>0) (FIG. 13/STEP 110).

On the other hand, in the case where it is determined that the state ofcharge SOC of the battery is less than the charge threshold value SOCth(FIG. 13/STEP 106 . . . NO), the current desired total heat generationamount Qmot_obj of the electric motors 31R, 31L is set as a sum of theprevious desired total heat generation amount Qmot_obj_p and aproportional value K′(SOCth−SOC) of a difference of the charge thresholdvalue SOCth and the state of charge SOC (K′>0) (FIG. 13/STEP 120).

On the basis of the above, it is determined whether or not the desiredtotal heat generation amount Qmot_obj is positive (FIG. 13/STEP 112).

In the case where it is determined that the desired total heatgeneration amount Qmot_obj is positive (FIG. 13/STEP 112 . . . YES), adesired heat generation amount Qmot_obj_R of the right electric motor31R (a desired right heat generation amount) and a desired heatgeneration amount Qmot_obj_L of the left electric motor 31L (a desiredleft heat generation amount) are set (FIG. 13/STEP 116). The desiredright heat generation amount Qmot_obj_R is set by multiplying the heatgeneration ratio r to the desired total heat generation amount Qmot. Thedesired left heat generation amount Qmot_obj_L is set by multiplying adifference between 1 and the heat generation ratio r (1−r) to thedesired total heat generation amount Qmot.

In addition, in the case where it is determined that the state of chargeSOC of the battery is less than the charge threshold value SOCth (FIG.13/STEP 106 . . . NO), both of the desired right heat generation amountQmot_obj_R and the desired left heat generation amount Qmot_obj_L may beset to zero.

In the case where it is determined that the desired total heatgeneration amount Qmot_obj is zero or negative (FIG. 13/STEP 112 . . .NO), the desired total heat generation amount Qmot_obj is reset to zero(FIG. 13/STEP 114), and the desired right heat generation amountQmot_obj_R and the desired left heat generation amount Qmot_obj_L areset as is explained above (FIG. 13/STEP 116). That is, in this case, thedesired right heat generation amount Qmot_obj_R and the desired leftheat generation amount Qmot_obj_L are both set to zero.

The control unit 50 sets the motor currents Imot_R, Imot_L of theelectric motors 31R, 31L, on the basis of the desired right heatgeneration amount Qmot_obj_R and the desired left heat generation amountQmot_obj_L, respectively, and the internal resistance rmot_R, rmot_L ofthe electric motors 31R, 31L (FIG. 13/STEP 118). In setting of thevalues, for example, relational expressions 15a, 15b are used.Imot_(—) R=(Qmot_obj_(—) R/rmot_(—) R)^(1/2)   expression 15aImot_(—) L=(Qmot_obj_(—) L/rmot_(—) L)^(1/2)   expression 15b

Thereafter, the control unit 50 controls the motor currents Imot_R,Imot_L of the electric motors 31R, 31L to conform to the set value.

(Functional Effect of the Vehicle of the Present Invention)

According to the vehicle 1 as the mobile device of the presentinvention, in the case where the temperature allowance of one of aplurality of the translational mechanism (the electric motors 31R, 31L)is larger than the temperature allowance of the other translationalmechanisms, the operating mode of a plurality of the translationalmechanisms are controlled so that the heat generation amount of the onetranslational mechanism becomes larger than the heat generation amountof the other translational mechanism.

To be more specific, a ratio of the heat generation amount of eachtranslational mechanism (the desired right heat generation amountQmot_obj_R and the desired left heat generation amount Qmot_obj_L) tothe total heat generation amount of a plurality of the translationalmechanisms (the desired total heat generation amount Qmot_obj) (“r” and“1−r”) is adjusted according to the difference of the temperatureallowance Tmot_suff_diff among each translational mechanism.

For example, in the case where the temperature allowance Tmot_suff_R ofthe right electric motor 31R is larger than the temperature allowanceTmot_suff_L of the left electric motor 31L, that is, in the case wherethe motor temperature allowance deviation Tmot_suff_diff is “negative”,the heat generation ratio is set to a value larger than 0.5 (refer toFIG. 14). By doing so, the desired right heat generation amountQmot_obj_R is set to a value larger than the desired left heatgeneration amount Qmot_obj_L (refer to FIG. 13/STEP 116).

On the other hand, in the case where the temperature allowanceTmot_suff_L of the left electric motor 31L is larger than thetemperature allowance Tmot_suff_R of the right electric motor 31R, thatis, in the case where the motor temperature allowance deviationTmot_suff_diff is “positive”, the heat generation ratio r is set to avalue smaller than 0.5 (refer to FIG. 14). By doing so, the desired leftheat generation amount Qmot_obj_L is set to a value larger than thedesired right heat generation amount Qmot_obj_R (refer to FIG. 13/STEP116).

Thereafter, the motor current of each motor is controlled so that themotor current and further the field current of the one motor havingrelatively large temperature allowance becomes larger than the motorcurrent and further the field current of the other motor havingrelatively small temperature allowance (refer to FIG. 13/STEP 118). As aresult, it becomes possible to avoid the situation where the batterycurrent Ibatt becomes positive in the state where there is a possibilityof the battery being overcharged. Further, the difference of thetemperature allowance Tmot_suff_diff between the electric motors 31R,31L as a plurality of the translational mechanisms is reduced, and thesituation where the temperature of a specific translational mechanismbeing remarkably higher than the other translational mechanisms isavoided.

Further, as the battery current Ibatt is larger, that is, as aconsumption allowance of the electric energy accumulated in an energyaccumulation component (battery) (state of charge SOC) is larger, thedifference between the ratio of the heat generation amount of eachtranslational mechanism (the desired right heat generation amountQmot_obj_R and the desired left heat generation amount Qmot_obj_L) withrespect to the total heat generation amount by a plurality of thetranslational mechanisms (the desired total heat generation amountQmot_obj) (“r” and “1−r”) is set to be smaller (refer to FIG. 14).Therefore, as the state of charge SOC of the battery is larger, thedifference of the heat generation amounts Qmot_R, Qmot_L between theelectric motors 31R, 31L is reduced. By doing so, it becomes possible toavoid the situation where the energy consumption volume and further theheat generation amount of a part of the translational mechanisms among aplurality of the translational mechanisms become excessive compared tothe other translational mechanisms.

As a result, frequency of the temperatures Tmot_R, Tmot_L of eachelectric motors 31R, 31L elevating to a temperature high enough topromote shortening of the heat deterioration lifetime is decreased. As aresult, it becomes possible to extend the heat deterioration lifetime ofeach of the electric motors 31R, 31L.

Because the electric motors 31R, 31L as a plurality of the translationalmechanisms are configured from the same specification, and the operatingmode of each of the electric motors 31R, 31L and the relationship of theheat generation amounts Qmot_R, Qmot_L are common, it becomes possibleto easily adjust the heat generation amounts Qmot_R, Qmot_L of theelectric motors 31R, 31L according to differentiation of the operatingmode of each of the electric motors 31R, 31L and the like.

Further, the common traveling motion unit 5 is driven by a plurality ofthe translational mechanisms (the electric motors 31R, 31L), but theextension of the heat deterioration lifetime of each of a plurality ofthe translational mechanisms may be obtained as is explained above.Therefore, it becomes possible to decrease the frequency of disablementof the traveling motion unit 5 from disablement of a part of a pluralityof the translational mechanisms, and further the disablement of thevehicle 1 as the mobile device.

(Other Embodiments of the Present Invention)

Next, explanation will be given on other embodiments of the mobiledevice of the present invention explained above.

As another embodiment of the mobile device of the present inventionwhich differs from the vehicle 1 of a configuration as shown in FIG. 1and FIG. 2, any mobile device configured to be in translational motionby an actuation of a translational mechanism or a plurality of actuatorsas a constituent component thereof may be adopted.

To be more specific, the wheel assembly 5 serving as the travelingmotion unit of the vehicle 1 in the above-explained embodiments has theone-piece construction. Alternatively, however, the wheel assembly 5 mayhave a construction shown in, for example, FIG. 9 of the aforesaidpatent document 3. More specifically, the wheel assembly may beconstructed to have a rigid annular shaft member and a plurality ofrollers rotatively and externally inserted into the rigid annular shaftmember such that the axial centers thereof are oriented in thetangential direction of the shaft member, the plurality of these rollersbeing arranged in the circumferential direction along the shaft member.

Further, the traveling motion unit may have a crawler-shaped structure,as shown in, for example, FIG. 3 of patent document 2.

Alternatively, as shown in, for example, FIG. 4 of the aforesaid patentdocument 2, FIG. 6 of patent document 3, or FIG. 1 of patent document 1,the traveling motion unit may be constructed of a spherical member, andthe vehicle may be constructed such that the spherical member isrotatively driven in a direction about the X-axis and a direction aboutthe Y-axis by an actuator (e.g., an actuator having the aforesaid wheelassembly 5).

Further, in the above-explained embodiments, the vehicle 1 provided withthe seat 3 as the boarding section for an occupant has been exemplified.Alternatively, however, the inverted pendulum type vehicle in accordancewith the present invention may be a vehicle having a constructionwherein a step on which an occupant rests his/her both feet and asection to be gripped by the occupant standing on the step are mountedon a base body, as illustrated in, for example, FIG. 7 in patentdocument 3.

Thus, the present invention can be applied to inverted pendulum typevehicles of various constructions, as illustrated in the aforesaidpatent documents 1 to 3 and the like.

Further, the inverted pendulum type vehicle in accordance with thepresent invention may be provided with a plurality of traveling motionunits (e.g., two in the lateral direction, or two in the fore-and-aftdirection, or three or more) capable of traveling in all directions on afloor surface.

Further, the inverted pendulum type vehicle in accordance with thepresent invention may be an inverted pendulum type vehicle of a formwith an object payload supporting part being tillable about one-axis(for example, about an axis in a lateral direction of an occupantboarding the vehicle), and traveling the vehicle in the fore-and-aftdirection of the occupant in accordance with the tilting thereof.

Further, the inverted pendulum type vehicle of the above-mentionedembodiment is a vehicle equipped with a payload supporting part (seat) 3for the occupant as an object loading unit, however, it may be equippedwith a loading unit for loading a target object for transportation suchas a package, in place of the payload supporting part 3 for an occupant.In this case, the control process similar to the boarding mode may beexecuted in the state where the target object for transportation isloaded on the loading unit, and the control process similar to theautonomous mode may be executed in the state where the target object fortransportation is not loaded.

In the above-mentioned embodiment, two electric motors 31R, 31L(translational mechanisms) are provided to the vehicle 1 for activatingthe common traveling motion unit 5, however, three or more translationalmechanisms for activating the common traveling motion unit may beprovided to the vehicle (refer to Patent Document 1).

In the above-mentioned embodiment, specification of the electric motors31R, 31L (translational mechanisms) are identical. However, as anotherembodiment, at least a part of the specification of a plurality of thetranslational mechanisms may differ from each other. In this case, theheat capacity Cmot_R of the right electric motor 31R and the heatcapacity Cmot_L of the left electric motor 31L normally differ. Takingthis point into consideration, the heat generation ratio function may bedefined so that the value becomes Cmot_R/(Cmot_R+Cmot_L) and not 0.5, inthe case where the temperature allowance deviation Tmot_suff_diff iszero, that is, in the case where the temperature allowance Tmot_suff_Rof the right electric motor 31R and the temperature allowanceTmot_suff_L of the left electric motor 31L are equal (refer to FIG. 14).

It may be set so that the control unit 50 controls the operating mode ofat least one translational mechanism so as to decrease the heatgeneration amount of the at least one translational mechanism, and aswell as actuates a braking mechanism (the mechanical brakes 34R, 34L),taking the existence of a temperature allowance or a heat accumulationallowance as a requirement.

A second temperature threshold value that becomes a calculation standardof the temperature allowance of the braking mechanism normally differsfrom the temperature threshold values Tmot_th_R, Tmot_th_L that are thecalculation standard of the temperature allowance of the translationalmechanisms (the electric motors 31R, 31L). Further, a second heataccumulation threshold value that becomes a calculation standard of theheat accumulation allowance of the braking mechanism normally differsfrom heat accumulation threshold values Qmot_res_th_R, Qmot_res_th_Lthat are the calculation standard of the heat accumulation allowance ofthe translational mechanisms (the electric motors 31R, 31L).

According to the mobile device of the above-mentioned configuration,change in the translational mode of the mobile device (vehicle 1) inaccordance with the change in the operating mode of a plurality of thetranslational mechanisms so as to decrease the heat generation amount ofat least one translational mechanism may be adjusted by the operation ofthe braking mechanism having temperature allowance or heat accumulationallowance. That is, the translational mode of the mobile device may becontrolled so that the decrease in the temperature allowance or the heataccumulation allowance of at least one translational mechanism issubstituted by the decrease in the temperature allowance or the heataccumulation allowance of the braking mechanism. For example, the motorcurrents Imot_R, Imot_L are controlled so that a rotating torques of therotating members 27R, 27L by the electric motors 31R, 31L are increasedas much as the increase in braking torques of the rotating members 27R,27L by the mechanical brakes 34R, 34L.

By doing so, the difference in the temperature allowance or the heataccumulation allowance between a plurality of the translationalmechanisms is reduced, so that a decrease in the frequency of thetemperature of each of a plurality of the translational mechanisms fromelevating to a temperature high enough to promote shortening of the heatdeterioration lifetime may be obtained. As a result, it becomes possibleto extend the heat deterioration lifetime of each of the translationalmechanisms.

The invention claimed is:
 1. A mobile device equipped with an energyaccumulation component, a plurality of translational mechanisms fortranslational movement of the mobile device which actuate by consumingenergy accumulated in the energy accumulation component, a firsttemperature measurement component configured to measure or estimatetemperature of each translational mechanism, and a control deviceconfigured to control operation of each translational mechanism, furthercomprising an energy remaining amount measurement component configuredto measure or estimate an energy remaining amount of the energyaccumulation component, wherein the control device is configured tocontrol operating mode of each translational mechanism, in accordancewith a temperature allowance of each translational mechanism which is adifference between a temperature of each translational mechanismmeasured or estimated by the first temperature measurement component inthe state being smaller than a first temperature threshold value and thefirst temperature threshold value, or a sum of the difference and aproportional values of a temporal change rate of the difference, so thata heat generation amount of one translational mechanism having largetemperature allowance compared to other translational mechanisms becomeslarger compared to the heat generation amounts of other translationalmechanisms, wherein the control device is further configured to controlthe operating mode of each translational mechanism so that a differencebetween a ratio of the heat generation amount of the one translationalmechanism with respect to a total heat generation amount of a pluralityof the translational mechanisms and a ratio of the heat generationamounts of the other translational mechanisms with respect to the totalheat generation amount of a plurality of the translational mechanismsbecomes larger, as a difference between the temperature allowance of theone translational mechanism and the temperature allowance of the othertranslational mechanisms becomes larger, and wherein the control deviceis further configured to control the operating mode of each of aplurality of the translational mechanisms, respectively, so that thedifference between the ratio of the heat generation amount of the onetranslational mechanism with respect to the total heat generation amountof a plurality of the translational mechanisms and the ratio of the heatgeneration amounts of the other translational mechanisms with respect tothe total heat generation amount of a plurality of the translationalmechanisms becomes smaller, as the energy remaining amount measured orestimated by the energy remaining amount measurement component becomeslarger.
 2. The mobile device according to claim 1, wherein a pluralityof the translational mechanisms are configured from identicalspecification.
 3. The mobile device according to claim 1, furthercomprising a traveling motion unit which actuates a translational forceof the mobile device with respect to a floor surface, while in contactwith the floor surface, wherein the mobile device is configured so thatthe common traveling motion unit is driven by a plurality of thetranslational mechanisms.
 4. A mobile device equipped with an energyaccumulation component, a plurality of translational mechanisms fortranslational movement of the mobile device which actuate by consumingenergy accumulated in the energy accumulation component, a firsttemperature measurement component configured to measure or estimatetemperature of each translational mechanism, and a control deviceconfigured to control operation of each translational mechanism, furthercomprising a braking mechanism which actuates to brake a translationalmotion of the mobile device, and a second temperature measurementcomponent configured to measure or estimate a temperature of eachbraking mechanism, wherein the control device is configured to controloperating mode of each translational mechanism, in accordance with atemperature allowance of each translational mechanism which is adifference between a temperature of each translational mechanismmeasured or estimated by the first temperature measurement component inthe state being smaller than a first temperature threshold value and thefirst temperature threshold value, or a sum of the difference and aproportional values of a temporal change rate of the difference, so thata heat generation amount of one translational mechanism having largetemperature allowance compared to other translational mechanisms becomeslarger compared to the heat generation amounts of other translationalmechanisms, and wherein the control device is further configured tocontrol the operating mode of at least one translational mechanism sothat the heat generating amount of the at least one translationalmechanism decreases, and as well as to actuate the braking mechanism,taking the existence of a temperature allowance of the braking mechanismwhich is a difference between a temperature of the braking mechanismmeasured or estimated by the second temperature measurement component inthe state being smaller than a second temperature threshold value andthe second temperature threshold value, or a sum of the difference and aproportional value of a temporal change rate of the difference, as arequirement.
 5. A mobile device equipped with an energy accumulationcomponent, a plurality of translational mechanisms for translationalmovement of the mobile device which actuate by consuming energyaccumulated in the energy accumulation component, a first temperaturemeasurement component configured to measure or estimate temperature ofeach translational mechanism, and a control device configured to controloperation of each translational mechanism, wherein the control device isconfigured to control operating mode of each translational mechanism, inaccordance with a temperature allowance of each translational mechanismwhich is a difference between a temperature of each translationalmechanism measured or estimated by the first temperature measurementcomponent in the state being smaller than a first temperature thresholdvalue and the first temperature threshold value, or a sum of thedifference and a proportional values of a temporal change rate of thedifference, so that a heat generation amount of one translationalmechanism having large temperature allowance compared to othertranslational mechanisms becomes larger compared to the heat generationamounts of other translational mechanisms, and wherein the controldevice is equipped with a desired total heat generation amountdetermination component configured to determine a desired total heatgeneration amount by the operation of a plurality of the translationalmechanisms, on the basis of the energy consumption amount of eachtranslational mechanism, a heat generation ratio determination componentconfigured to determine a heat generation ratio of each translationalmechanism in accordance with the temperature allowance of eachtranslational mechanism, and a desired heat generation amountdetermination component configured to determine a desired heatgeneration amount of each translational mechanism, respectively, byintegrating the heat generation ratio and the desired total heatgeneration amount, wherein the control device is further configured tocontrol the operation of each translational mechanism so that the actualheat generation amount coincides with the desired heat generationamount.